If you make changes to MusicBrainz Server, they'll need to go through our code review process. You'll need two things: somewhere to put the git branch, and a codereview account.
Get the latter at http://codereview.musicbrainz.org/.
For the former, we recommend github if you don't have your own git hosting already. Make an account, then fork https://github.com/metabrainz/musicbrainz-server -- after that, make your changes and push them back to github -- for small changes, you may be able to do them with github's integrated editor. Basic git usage I'll necessarily skip here; use google.
Finally, generate a diff: 'git diff master...HEAD' piped into a file (e.g. 'git diff master...HEAD > blah.diff') should do it, presuming you haven't done anything strange. Upload this file to codereview after hitting the new review button. Fill in the other details, such as the branch name; note in the description where your repository is (your github account, if you used that recommendation). Also note what testing and such things you did -- those reviewing your code will want to know.
Ultimately, you should get some "Ship It"s or comments of things to fix; fix anything that needs fixing, and discuss with those who comment on your review. Once it's satisfactory, someone with access to the official git will merge your code and it'll get released!