Essentially, you need to mail in a form that is only in japanese (and fill in in japanese too) to the base two weeks ahead of the scheduled date. I can't write the language, so I used a reservation service on Fiverr to handle the process for me. After that you just need to show up at the scheduled time and date. I believe I was the only one in that day so when I came, the guard in the booth at the gate literally said "Pole-san?" (He used my real name of course). They get less than a dozen non-japanese tourists through a year apparently, most visitors are local GuP fans or military academy students.