Licenses

[Javichino]

I want to make a site to sell software online and with nBill generate and sell licenses for them, but I nBill is complicated and does not understand how to use it, help me?

something very similar to this:
http://www.nbill.co.uk/component/option,com_netinvoice/Itemid,8/action,orders/task,order/cid,1/