# Adding the AD library to your PowerShell Session.
Add-Type -Path 'C:Program FilesMicrosoft Azure Active Directory ConnectMicrosoft.IdentityModel.Clients.ActiveDirectory.dll'

# This is the tenant id of you Azure AD. You can use tenant name instead if you want.
$tenantID = "<the tenant id of Azure AD>"
$authString = "https://login.microsoftonline.com/$tenantID"

# Here, the username must be MFA disabled, and must not be a live id.
$username = "<the username of the AD's owner>"
$password = "<the password of the above user>"

# The resource URI for your token.
$resource = "https://graph.windows.net/"

# This is the common client id.
$client_id = "1950a258-227b-4e31-a9cf-717495945fc2"

# Create a client credential with the above common client id, username and password.
$creds = New-Object "Microsoft.IdentityModel.Clients.ActiveDirectory.UserCredential" `
                    -ArgumentList $username,$password

# Create a authentication context with the above authentication string.
$authContext = New-Object "Microsoft.IdentityModel.Clients.ActiveDirectory.AuthenticationContext" `
                    -ArgumentList $authString

# Acquire access token from server.
$authenticationResult = $authContext.AcquireToken($resource,$client_id,$creds)

# Use the access token to setup headers for your http request.
$authHeader = $authenticationResult.AccessTokenType + " " + $authenticationResult.AccessToken
$headers = @{"Authorization"=$authHeader; "Content-Type"="application/json"}

# Get the users.
Invoke-RestMethod -Method GET -Uri "https://graph.windows.net/$tenantID/users?api-version=1.6-internal"