If you mean on the cart here on IMVU mafias you have to check out your order, then you'll receive the bill you have to pay and after the payment you'll have to wait for the deliver. The person who delivers the merch is the one who placed the offer on here. For ex. I'm a creator with my IMVU account so I make my credits thanks to my activity, I place an offer on here, I get the request, get the bill paid (in which the buyer sent me the nickname of the avi I have to deliver the credits) and then I simply transfer those credit from my avi to the one indicated. The same works for all the other things. The forum offers a safe place for the seller to sell their stuffs and for the people who's interested to buy them.
Hope I'd helped you out!