1)Buy it from a class 3 dealer
2)Fill out a Form 4 in duplicate.
3)Get your chief LEO (police chief or sheriff) to sign off the form 4.
4)Submit the form 4, two passport photos, and two sets of fingerprints, and $200.00 to the ATF.
5)Wait about 6 to 8 weeks.
6) If everything is OK, when the Form 4 comes back to your dealer, pick it up and the suppressor. If it's not OK, you get your $200 back.
Do you have to agree to allow Feds access to your weapons at any time, or something to this effect? What reason did you give for wanting one (do they ask?).