You can't. Every commit must be reviewed and then pushed by a ports committer.
Regarding github, this is a read-only mirror. Although the current policy seems to be to accept pull requests there, the better way to get your commit reviewed and pushed is by opening a PR on
https://bugs.freebsd.org/ and attaching your commit (plain patches are fine, I personally prefer a full commit as produced by
git format-patch).
The issue with github pull requests (IMHO, no official statement!) is that it's a) another channel you won't necessarily observe as a committer, and b) tedious to work with as you have to fetch the patch/commit manually and apply it to your tree to be able to push it to the official repo.
BTW, what it actually means to be a maintainer is that you're responsible for the content of your port and your approval will be necessary for any change that isn't covered by one of the "blanket approvals".
If you want to learn more, there's the
Committer's guide available, it can also help you to create commits and commit messages that can be committed "as is" without anyone needing to edit anything.
