J@CKY

Can you please give more details?
I assume you guys has already jailbroken your device.

I prefer using installous to install ipa file, not itunes. It never disappointed me.
if you have not yet got installous, go to cydia and install it, add http://cydia.hackulo.us/ as source and you'll find it.

Then, transfer the ipa file to installous download folder, using SSH or USB, any method of your choice.  I recommend using iFunbox, easy and quick.

the default location of installous download folder is //User/Documents/Installous/Downloads/

Then you can see the file when install the ipa without any difficulty using installous.