If you want to push to github, you first have to create an access token. Preferably create a fine-grained access token (https://docs.github.com/en/authentication/keeping-your-account-and-data-secure/managing-your-personal-access-tokens#creating-a-fine-grained-personal-access-token) as general personal access tokens are a security risk. Then when you want to push e. g. like this

git push -u origin main

you will be asked to provide a username and a password. As username type in your github user name and instead of your github password you enter the fine grained access token.