If when the order was made you used your own details and account for the purchase, but just used your friends credit card details, then you can simply register the products into your own Member Account as normal.
However if the purchases were registered to the name of your friend and the Member Account setup in his name then you will need to contact Customer Support to get this changed.
Please use the link below if you need to request help from Customer Support.
http://www.reallusion.com/CustomerSupport/User/QForm.aspx
Peter EdwardsForum Administrator
www.reallusion.com