Well, normally since I am not a dependent of a military member or in the military myself, I can't just go into a PX and buy stuff, isn't that the whole point of the boot letter (to prove i'm an appointee)?
That's what I gather.
The letter may also grant you permission to enter the post or base.
One correction, however. The boots are not sold at the PX or BX -- that's where you find all the civvie stuff. When the time comes, you want to go to Clothing Sales. They'll have anything and everything that curren airmen/soldiers/sailors need for their uniforms.
Yes. You can to to the post PX. The sales people in the shoe dept. Will be very helpful. They will fit you and show you the boot choices. There are a couple of different manufacturers available. Bring your boot letter that authorizes you to make the purchase.
You can go to the nearest Army post. The "boot letter" will authorize your son/daughter to purchase the boots and shoes on post. Bring cash because they won't take your debit/credit card if you aren't military.