If you have created the account in WHM as using the domain that you have bought, all you need to do it set the nameservers for the domain to be the correct ones for the server your reseller account is on.
If you want to retain control of your DNS and only use the created account for web access then you need to create a new A record for your domain name pointing to the IP address of the server your reseller account is on. Best to create one for
www.domain.com and domain.com if you want both to point to the website.