my-second-powershell-script.ps1

$client_id = "<YOUR-CLIENT-ID>"
$client_secret = "<YOUR-CLIENT-SECRET>"
$redirect_uri = "<YOUR-CALLBACK-URL>"

$authz_endpoint = "https://graph.facebook.com/oauth/authorize"
$token_endpoint = "https://graph.facebook.com/oauth/token"

open ($authz_endpoint + "?client_id=" + $client_id + "&redirect_uri=" + $redirect_uri)

$code = Read-Host "code"

$params = @{
  client_id = $client_id;
  client_secret = $client_secret;
  code = $code;
  grant_type = "authorization_code";
  redirect_uri = $redirect_uri;
}

$result = Invoke-RestMethod -Uri $token_endpoint -Method Post -Body $params

$result.access_token