Start QT Player and import the file you want to convert.
Choose 'Export' from the file menu
Select 'Movie to MPEG-4' from the selection at the bottom of the Save dialogue window that appears.
Click on 'Options' beside the 'Export' pop-up selections
In the sub-window that appears choose 'H.264' in the Video Format selection menu.
From there you can choose the rest of your movie setup prefs.
Please make a note in your posts if you decide to post the same question to multiple forums. That way the the folks answering you aren't wasting their time if someone else has already given you a correct response.