Copy Video from Mac to iPhone
Depends on how you plan to play it on the iPhone. Both following ways require iTunes and an iPhone connected to it by cable or wireless.


If you want to copy it to your Media library and play it natively you will need to:


Select your device
Click on Movies tab
Check Sync Movies and check the desired movie from your iTunes library

If you use an app (such as VLC) to play it you will need to:


Select your device
Click on Apps tab
Scroll to File Sharing and select desired app from list
Press on Add.. button and select desire movie from file chooser dialog



Alternately, you can share/stream your movie to your iPhone over wireless connection if you don't want to take it with you.