Navigate to the plugin configuration page, click the "Add New Provider" button (located either in the middle or top-right corner), select GitLab as the application, and copy the callback URL from the plugin and keep it handy, as you'll need it to configure GitLab as the OAuth provider.
Login to Gitlab : Go to GitLab or your on-premise GitLab Server and login to your account.
Navigate to your profile settings.
Create app : Select applications in left menu.
Provide the required details.
Name :
This can be anything. Consider something like <Organization>'s GitLab or <Your Name>'s GitLab or something else descriptive.
Redirect URI :
Copy Callback URL from plugin.
NOTE: The check-box for “api” needs to be checked, as it’s unchecked by default.
Get Client ID & Client Secret : Copy Application Id , Secret and Scope.