Go to a class III shop that has suppressors for sale, fill out the application to BATF get the all the needed signatures, the shop will put the serial number on the application, you will have to pay for it or leave a deposit. Send to BATF, wait , then wait, then wait somemore. The approval stamp, and it is a stamp, along with the application approval will someday come back. Then the shop will release your suppressor to you. In the mean time get the proper threaded barrel for the firearm with the proper thread count that matches the suppresor ready to go. Purchase sub-sonic ammo if possible. Oh don't forget the $200.00 check to BATF that they will cash in less then 24hrs. While you wait, and then wait, then wait somemore.