Hi Samantha,
I just verified this option is still available so you should be able to accomplish this by checking the bubble next to "Flat Rate Shipping" and then choosing the "Other(see item description)" option from the shipping service pull-down menu. If you require further assistance with this matter, please file a support request using the appropriate link on our help page:
http://www.auctiva.com/free_auction_software_help/help.aspx
-Mike