Q: how to use bluetooth between two iphones

You don't.

This has never been a featire of iphone.

If the two devices are iphones, you can use air drop.

this is what ios support in terms of bluetooth

http://support.apple.com/kb/HT3647?viewlocale=en_US&locale=en_US

You can't. Apple doesn't allow you to share files via Bluetooth. Like someone here said, if you have an iPhone 5 or above, use airdrop. There are a lot of 3rd party apps that allow you to share stuff by one way or another. Check out the AppStore if you're desperate.