This seems like it should be straightforward, but I found the documentation confusing.
gh needs to know which project you want to create a PR against. You can set this once in your repository:
gh repo set-default wolfi-dev/os
The gh command does not seem to want to push code for you without interactively prompting. So you need to this on your own:
git push my-remote
The gh command needs to know where to find that pushed code. It does so by looking at your branch's upstream setting, so you need to make sure that exists:
git branch --set-upstream-to my-remote/my-branch
Now gh has everything it needs to know, and can create a PR w/o prompting:
gh pr create -f