Domain Mapping with Direct Admin

I succesfully installed "domain mapping" plugin, but after mapping domain just nothing happens. I guess i don't understand that part at "add a DNS "A" record pointing at the IP address of this server: XX.XX.XX.XXX"

I'm using DirectAdmin panel and already using wordpress MU with subdomains.

WP MU instalation and domain at wich i want to map domain is on the same server