How do you change the name servers?
If you're unsure you should contact your domain registrar. This is out of the scope of MyBB support.
Because I am nice:
-You obtain Namservers from your hosting provider. (Example, Host4Posts are ns1 and ns2.h4p.us
-Go to Registrars site
-choose domain
-Choose "Modify Nameservers"
-Enter Nameservers
-Hit Apply
-Wait up to 48 hours