Sample Powershell script to connect and use Microsoft Graph API

GraphAPI Example.ps1

#You need AzureAD Module (Save-Module AzureAD -Path C:\temp)
function GetAuthHeaders
{
    [cmdletbinding()]
    param(
[Parameter(Mandatory = $true)]
    [string]$Tenant = "",
[Parameter(Mandatory = $true)]
    [string]$UserPrincipalName = ""
    )
    $ScriptDir = "C:\temp"
	$AzureADModulePath = join-path $ScriptDir "\AzureAD"
    $job = Start-Job -ArgumentList $AzureADModulePath ,$Tenant,$UserPrincipalName -ScriptBlock {
        $AzureADModulePath = $args[0]
        $Tenant = $args[1]
        $UserPrincipalName = $args[2]

        $adal = "$AzureADModulePath\Microsoft.IdentityModel.Clients.ActiveDirectory.dll"
        $adalforms = "$AzureADModulePath\Microsoft.IdentityModel.Clients.ActiveDirectory.Platform.dll"
        $tMod = [System.Reflection.Assembly]::LoadFrom($adal)
        $tMod = [System.Reflection.Assembly]::LoadFrom($adalforms)
        
        [string] $clientId = "1950a258-227b-4e31-a9cf-717495945fc2"
        [string] $authority = "https://login.microsoftonline.com/$Tenant"
        [uri] $redirectUri = "urn:ietf:wg:oauth:2.0:oob"
        [string] $resourceURI = "https://graph.microsoft.com"
        $authContext = New-Object "Microsoft.IdentityModel.Clients.ActiveDirectory.AuthenticationContext" -ArgumentList $authority
        $PromptBehavior = [Microsoft.IdentityModel.Clients.ActiveDirectory.PromptBehavior]::Auto
        $platformParam = New-Object "Microsoft.IdentityModel.Clients.ActiveDirectory.PlatformParameters" -ArgumentList $PromptBehavior
        $userId = New-Object "Microsoft.IdentityModel.Clients.ActiveDirectory.UserIdentifier" -ArgumentList $UserPrincipalName, "OptionalDisplayableId"
        $authResult = $authContext.AcquireTokenAsync($resourceUri, $clientId, $redirectUri, $platformParam, $userId)
        $AuthHeader=$authResult.result.CreateAuthorizationHeader()

        $headers = @{
            "Authorization" = $AuthHeader
            "Content-Type"  = "application/json"
        }
        
        Return $headers
    }
    $Wait = Wait-Job $job
    $jobResult = Receive-Job $job
    Return $jobResult
}


$Tenant = "TENANTNAME.onmicrosoft.com"
$UserPrincipalName = "user@TENANTNAME.onmicrosoft.com"
$authheader = GetAuthHeaders -Tenant $Tenant -UserPrincipalName $UserPrincipalName
$uri ="https://graph.microsoft.com/v1.0/me/"
#$URI = "https://graph.microsoft.com/v1.0/reports/getMailboxUsageDetail(period='D7')"
$response = Invoke-RestMethod -Uri $uri -Headers $authHeader -Method Get
$response