See the online documentaion: Single Machine | Multi-Machine | Kubernetes
Go to your GiHub profile setting and click OAuth applications
under Developer settings
menu on left sidebar.
You will see the following register page.
Please make sure that your drone Authorization callback URL
setting. It is very import the authorization callback URL matches your http(s) scheme and hostname exactly with /authorize (0.8) /login (1.0) as the path.
Copy Client ID
and Client Secret
Open your drone home page in your browser and login as Github account.