Like webfreak said

"Your host should provide you with nameservers. You can then update your domain's nameservers at your registrar."

Basically when you get your hosting, they will most likly send you an email. That email will have all the details needed and a area that will say NS or DNS (nameservers). They should be like ns1.name.com or dns1.name.com... Basically you copy those and when you purchase your domain, you paste the exact ones they give you. Then you wait from 12-72 hrs and the domain will point to your hosting account

If you need more details or extra help, free free to ask us here anytime

Good luck number6