Need help to customize site creation registration


I'm using pro sites to sell MicroSites. There are no free site. Only 1 premium subcription level.

I found some information related to my Blog Template to customize the registration process but it does not seems to work and I must admit, I barley understand the instruction. My goal is to be able to provide a lot of text on the registration to explain what to fill in the field. Because the userid and the url must be the same, which is their already-defined Member ID from the GetEasy "club". This ID is defined on another Web site. I want to ask them for this ID and fill the url with it.