I got to the point where I figured out how to input a message, but what serves as the signature? My forum name, a set of numbers? What should I input on the message? Forgive me, but I have never sent a signed message using this feature.
In your Bitcoin client, double-click the payment transaction, and copy the transaction ID. Visit http://blockexplorer.com/tx/[your transaction ID]. On that page, copy the top "From address". Enter that in the top field under File->Sign Message.
The program will verify that you own the private key to that address, and generate a signature for the message you typed in, which should include your shipping address.
@ tvbcof and Klestin thanks.
I still don't understand the mechanisms involved.
To be honest there should be an illustrated video highlighting how this works and how to use the feature.
I think I got it, however I have multiple from addresses, i presume it is ok to just enter 1 of them to generate the message?
correct you just have to maintain ownership of the address you sign with as long as you need to lay claim to the payment.
haha im not actually serious cause thats a lot to ask for... 
consume? 
given the size of the smallest flatrate box, i wasn't planning to use them. even for twenty units, it's excessive space. i'll make a custom box with some foam for padding.