You choose an FFL to have buds ship the gun to during checkout, your chosen FFL will contact you after your gun has arrived, then you will go in and fill out your background check, and the they will also complete the transfer after the background check comes back clear.
It will be the receiving ffl that does all transfer and background checks
Full details here
budsgunshop.com/howtobuy.php

Mark, your selected local FFL Dealer does you Form 4473 and background check preceding the transfer of the firearm to you and payment of the transfer fee Sir. Cheers and stay safe!

Mark, your FFL whom you have the gun shipped to will do your background check.