do i need to create an 'A NAME' or CNAME ?? and how ??

hi @wpmu i need help,
i have:

mu domain > http://www.mudomain.com

client subdomain > clientdomain.mudomain.com

client domain > http://www.clientdomain.com

i need to map domain: http://www.clientdomain.com

- do i need to create an 'A NAME' or CNAME from my 'client domain'?? (in my hosting cpanel)

[i need step-by-step assistance]