Step by step guild to using power shell to get a Google access token.

GmailSendMail.psi

clear-host;
#Remove-Variable * -ErrorAction SilentlyContinue
#get-item Variable:*
 #Get-Variable | Select-Object -ExpandProperty Name
 . C:\Users\linda_l\Desktop\PowerShell\GoogleOauth.ps1

Add-Type -Path "C:\Users\linda_l\Documents\visual studio 2015\Projects\TestingLibrary\packages\AE.Net.Mail.1.7.10.0\lib\net45\AE.Net.Mail.dll"
Add-Type -AssemblyName System.IO
Add-Type -AssemblyName System.Text.Encoding

$clientId = "46123799103-d0vpdthl4ms0soutcrpe036ckqn7rfpn.apps.googleusercontent.com";
$secret = "pj6hx1H2N5BFqdnaNhIbie";


#$AuthURL = GetAuthURL $clientId "https://mail.google.com/"
#Write-Host "Google Auth URL: " $AuthURL;
#$code = "4/IUVt9ULs5ZBX_Hd4pLQ2LyuE8xgNWjiCfCUKA1BZMGQ";
#ExchangeCode  $clientId $secret $code

$refreshToken = "1/Wo0UO4_dYY2z6BJ3idi9WaHR838FJ19XU0-p7j1Rtzs";

$accessToken = RefreshAccessToken  $clientId $secret $refreshToken

function Base64UrlEncode([string]$msgStr2) 
{
    $inputBytes =  [System.Convert]::ToBase64String([System.Text.Encoding]::UTF8.GetBytes($msgStr2));
    # Special "url-safe" base64 encode.
    $inputBytes = $inputBytes.Replace('+', '-').Replace('/', '_').Replace("=", "");    
    return $inputBytes;
}


$email = new-object MailAddress("test@test.com");

$msg2 = new-object AE.Net.Mail.MailMessage;
$msg2.To.Add($email);
$msg2.Subject = "Your Subject";
$msg2.Body = "Hello , world from Gmail API!";
$msg2.From = $email;


$msgStr = new-object System.IO.StringWriter;
$msg2.Save($msgStr);

$encodedEmail = Base64UrlEncode $msgStr;
      
#Write-Host $encodedEmail;

Google Oauth Powershell

#  Setup:
#
#  Step 1: create new project on https://console.developers.google.com.
#  Step 2: Create oauth credentials type native or other.
#          Save the client id and secret. 
#  Step 3: Enable the api you are intersted in accessing.
#          Look up what scopes you need for accssing this api,
#  Step 4: Using the client id, and client secret from the 
#
#
# Inital Authenticate:  Authentication must be done the first time via a webpage create the link you will need.  More then one scope can be added simply by seporating them with a comama
#     Place it in a webbrowser. 
#
#    https://accounts.google.com/o/oauth2/auth?client_id={CLIENT ID}&redirect_uri=urn:ietf:wg:oauth:2.0:oob&scope={SCOPES}&response_type=code
#
#    Copy the authencation code and run the following script.  
#      note: AuthorizationCode can only be used once you will need to save the refresh token returned to you.  


$clientId = "{CLIENT ID}";
$secret = "{SECRET}";
$redirectURI = "urn:ietf:wg:oauth:2.0:oob";
$AuthorizationCode = '{Code from web browser link above}'; 

$tokenParams = @{
	  client_id=$clientId;
  	  client_secret=$secret;
          code=$AuthorizationCode;
	  grant_type='authorization_code';
	  redirect_uri=$redirectURI
	}

$token = Invoke-WebRequest -Uri "https://accounts.google.com/o/oauth2/token" -Method POST -Body $tokenParams | ConvertFrom-Json

# Save this
$token.refresh_token  


##########################################################################################################################
#
# Using refresh token to get new access token
# The access token is used to access an api by sending the access_token parm with any request. 
#  Access tokens are only valid for about an hour after that you will need to request a new one using your refresh_token
#
##########################################################################################################################

$clientId = "{CLIENT ID}";
$secret = "{SECRET}";
$redirectURI = "urn:ietf:wg:oauth:2.0:oob";
$refreshToken = "{Refresh token from the authentcation flow}";

$refreshTokenParams = @{
	  client_id=$clientId;
  	  client_secret=$secret;
          refresh_token=$refreshToken;
	  grant_type='refresh_token';
	}

$refreshedToken = Invoke-WebRequest -Uri "https://accounts.google.com/o/oauth2/token" -Method POST -Body $refreshTokenParams | ConvertFrom-Json

$accesstoken = $refreshedToken.access_token

# This will work assuming you used the gmail scope I was just testing this
$messages = Invoke-WebRequest -Uri "https://www.googleapis.com/gmail/v1/users/me/messages?access_token=$accesstoken"-Method Get | ConvertFrom-Json

# Apperntly powershell 2.0 doesnt have Invoke-WebRequest we can also use Invoke-RestMethod
#
Invoke-RestMethod -Uri  "https://www.googleapis.com/gmail/v1/users/me/messages?access_token=$accesstoken" | select-object -expandproperty messages | format-table

Oauthtaketwo.psi

function GetAuthURL([string]$clientId ,[string]$scopes) {

    $hold = "https://accounts.google.com/o/oauth2/auth?client_id=$clientId&redirect_uri=urn:ietf:wg:oauth:2.0:oob&scope=$scopes&response_type=code";

    return $hold;
}


function ExchangeCode([string]$clientId,[string]$secret, [string]$code){

   $data = “code=$code&client_id=$clientId&client_secret=$secret&redirect_uri=urn:ietf:wg:oauth:2.0:oob&grant_type=authorization_code”;  
    try {

   $response = Invoke-RestMethod -Uri "https://accounts.google.com/o/oauth2/token" -Method Post -Body $data 

   } catch {
    # Dig into the exception to get the Response details.
    # Note that value__ is not a typo.
    Write-Host "StatusCode:" $_.Exception.Response.StatusCode.value__ 
    Write-Host "StatusDescription:" $_.Exception.Response.StatusDescription
    }


#4/regHkmE9-e8xrLsgnmSOqbsq3T-xrTAxyXelv21hoSs
}


function RefreshAccessToken([string]$clientId,[string]$secret, [string]$refreshToken){

   $data = "client_id=$clientId&client_secret=$secret&refresh_token=$refreshToken&grant_type=refresh_token"
   try {

       $response = Invoke-RestMethod -Uri https://www.googleapis.com/oauth2/v4/token -Method POST -Body $data 

      return $response.access_token;
       
       

   } catch {
    # Dig into the exception to get the Response details.
    # Note that value__ is not a typo.
    Write-Host "StatusCode:" $_.Exception.Response.StatusCode.value__ 
    Write-Host "StatusDescription:" $_.Exception.Response.StatusDescription
    }

   
}

Sorry this is all i have I dont use windows anymore as a daily driver so havent used power shell in ages. It should be the same though just follow the auth example and then check the documentation for how to send the commands to sheet.