Search for the group tid-cdsid-acs cse and make this group admin of the repository.
This is only for code created at SLAC and not for code from the community:
Still in the Settings page, click on the General link on the menu on the left.
Find the section Default branch. If it is not pre-release, change from main to pre-release. This is to avoid accidental clones starting at main and pull requests made at main.
Still in the Settings page, click on the Branches link on the menu on the left.
Click on Add branch protection rule.
For the main branch:
Branch name pattern: type main in this field.
Check these boxes:
Require a pull request before merging
Require approvals
Require conversation resolution before merging
Lock branch
Click on Save changes.
For the pre-release branch:
Branch name pattern: type pre-release in this field.