All Google Ads API calls must be authorized through OAuth2. OAuth2 enables your Google Ads API client app to access a user's Google Ads account without having to handle or store the user's login info.
The following steps must be completed to authorize requests to the Google Ads API.
Supporting materials are also available for related topics.
Getting familiar with OAuth2 internals for the Google Ads API.
Using the OAuth Playground to generate refresh and access tokens.