How is this NFA $200 tax stamp paid?

A check or money order made payable to the Bureau of ATF together with the application forms are to be mailed to:

National Firearms Act Branch
Bureau of Alcohol, Tobacco, Firearms and Explosives
P.O. Box 530298
Atlanta, GA 30353–0298.

Source ATF: https://www.atf.gov/firearms/qa/how-tax-paid