All you need to do is point your repositories to pull/push to github, for main repository it can be done using:
git remote set-url origin firstname.lastname@example.org:phpmyadmin/phpmyadmin.git
If you are using just read only access then use following:
git remote set-url origin git://github.com/phpmyadmin/phpmyadmin.git
For other repositories just replace last part of the URL with repository name (they have not changed).
Everything should work as before, pushes should be now faster, because all notifications are done in background on github and they don't block pushing.