Need Some Help Understanding The HPS/JTS Upgrade For The ACW Series

[2-81 Armor]

Maybe this has been addressed, and I've just missed it but I haven't discovered anything in a quick look here or over at the SDC.

My understanding is that it may be possible to update the HPS versions to the latest JTS version provided we get a SN from JTS after providing a proof of purchase. This makes sense to me, but I'm confused.

I can see that new official updates are now available for Antietam and Gettysburg. I own both of these (HPS versions) along with Chancellorsville and Peninsula (also HPS). I'd like to upgrade Antietam and Gettysburg now, and of course the other two as patches become available.

I'm probably missing the obvious, but what constitutes a proof of purchase (I certainly have the HPS CD's and cases, but it's been years, and I don't have any receipts or emails with order numbers any more) and what is the exact procedure to get a SN/Patch that works with the HPS version?

My apologies for asking something that might be totally obvious, but I've never claimed to be the sharpest knife in the drawer.

Can someone help out by posting some instructions that even I can understand and follow?