How To Transfer apps to Iphone from my Computer?

Ok so (a friend of mine) downloaded apps from the internet and wants to know if there's any way to sync them to his iphone

P.S. In iTunes he has tried the following:

-Add a file to iTunes library
-Selected the file
-Selected the app from the "Apps" tab
-Pressed Sync

Upon doing this iTunes said it was syncing however on his iphone it said that the "app" had failed to install

Any help would be appreciated you can email me as well if need be and don't want to tell me on here
-Thanks

The apps will not sync to your phone as they are illegal apps. Only way to do so would be to jailbreak your iPhone and install a tweak called app sync. Which Will allow you to sync illegal apps to and from your computer.