It uses power from arduino.
I recommend you check if the library is compatible with your arduino and with other components you're going to use.
My project became much more complicated because after I done what I mentioned above, the receiving script stopped working properly,
so I had to reprogram it. And I turned into a slow script, that took around 3 seconds to verify if a message arrived... it was a problem
because the user was going to press a button just to verify if the message arrived.
If you can afford to buy a more expensive but compatible shield, do it.