I have a Github repository with an associated Github page (say, github.com/user/mypage), and I would like to include the URL to the Github page (say, user.github.io/mypage) in the About section of the repository. When I go to "Edit repository details", the Github page already shows up in the "Website" field and cannot be changed (which is fine) but it is not displayed in the About section. I've tried this with multiple repositories with associated Github pages, and all show the same behavior. Am I overlooking something blatantly obvious, or is it just not possible to include the URL here?
I tried for a week to link my GitHub Page to my GitHub repository. I just figured out how to do it and then found this post. I thought I would go ahead and post my answer. Doing so might be helpful by making this question more visible in future internet search results.
Click on the gear icon in the upper-right of your GitHub repository to the right of the word "About" (shown in the red circle below):

Paste the URL of your GitHub Page into the Website bar in the window that pops up. This Website bar will already contain text that is grayed-out and might match the URL of your actual GitHub Page. That grayed-out text is inactive. Go ahead and paste in the URL of your GitHub Page anyway. Then click Save changes. You are done. Your GitHub Page should now be linked to your GitHub repository.

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