IF they are legal in your state, and IF you submit the proper forms to the ATF after getting them signed by your local Sheriff or Police Chief along with your fingerprints and a $200.00 transfer tax, the ATF will send you a tax stamp for that particular suppressor (assuming you pass the BI). You need to go through this for every suppressor you own. Expect to wait 3 to 6 months.
However, owning a suppressor doesn't necessarily mean you can hunt with it...some states, even though they allow you to own a suppressor, do not allow you to hunt with one.