A little impatient aren't we? throwing attitude after less than 20 minutes is a little extreme for the middle of a work day.
Anyway, yes, you need register the domain with someone and then you also need a hosting service. I'm not sure when they say iWeb supports other domains that that means the iMac (or whatever the name of it is called) service will provide hosting services for an outside domain.
Someone like bluehost or godaddy can provide you with both services.