I haven't used anything but no-ip but extrapolating i'm gussing it's similar for other providers. You basically neet to setup DNS hosting, choosing the IP address to which the domain resolves to. What company is doing your web hosting ? If they have a site maybe I can take a look.

It might be the case where you have just registred the domain but that company does not provide DNS hosting. Then you'll need another service (like no-ip.com offers) where they just do the DNS hosting. If this is the case then there's another option where you do your own dns hosting but that's pretty advanced and I don't know much about it.