alwayseavesdropping on "Mapped domain doesn't seem to work (it's probably my fault)"

Thanks very much -- but the problem continues. I can't find where to change the nameservers. The support I've been reading says I should check with my "domain registrar," but I bought the domain through WordPress. I didn't go to any external site. Where do I go to change the name servers if I just clicked on wordpress "Buy this domain?"