Repository administrators can enforce required reviews so that pull requests must have at least one approved review before they are merged.
Note: Before enabling required reviews on a branch, you must first set the branch up as a protected branch.
On GitHub, navigate to the main page of the repository.
Under your repository name, click Settings.
In the left menu, click Branches.
Under Protected Branches, select the branch you want to restrict using the drop-down menu.
Select Require pull request reviews before merging.
Optionally, if the repository is part of an organization, select Restrict who can dismiss pull request reviews to search for and select the people or teams who can dismiss pull request reviews. This option is not available for personal repositories.
Optionally, select Include administrators. This enforces the required status checks on the repository administrators.
Click Save changes.