app “failed to instal”” to iphone

i downloaded partly cloudly to my itunes and when i drag it over to my iphone it says ” failed to install”. it will get 3/4 of the bar completed and then say it. Im not sure if my phone needs to be jailbroken or not, but thought i would ask.
If it does need to be, is there anyway i can download apps to my iphone?
Answer #1
jailbreak it
Answer #2
if its a ipa file you got off here or the internet yea its needs to be jailbroken..