I'm such a newbie. I just got a domain name to my ebay store (been using the one Activa free one) and I click on the domain link and says that it doesn't exit. But it does take me to ebay to search the store pages. I guess I'm in need of serious help.

Presume you mean 'exist' not 'exit' I would contact the supplier of the domain name, if it was Auctiva file a support request.

A new domain name make take a few days between paying/registering and it becoming active.