How do my clients access cpanel?

Your clients can access cpanel any number of ways:

1) through YOUR domain. http ://www.RESELLERDOMAIN.com/cpanel/

2) Through the server hostname: http ://www.server .hostname.com/cpanel/ (the server host name is in your setup email)

3) If propagation has completed, they can reach it through http ://www.domain.com/cpanel/ .