Instructions
Contact a Federal Firearms License dealer. Make arrangements for the FFL to receive the firearm from the seller. The FFL decides whether or not to accept the firearm and how much he will charge the buyer for doing so. If he chooses to accept the firearm, the FFL provides the seller with a copy of his federal license.
Transfer the firearm to the FFL. This is the responsibility of the out-of-state owner after he negotiates with the FFL the method of receiving payment for the firearm. Shipping might be overnight with major carriers, or personally transported if distance allows. The FFL logs the firearm into his books.
Fill out Federal Form 4473 at the gun store. This form attests that you are not a criminal and have nothing in your background that should keep you from owning a firearm.
Pay fees. The FFL needs to be paid for the cost of the firearm, tax and any transfer fee.