Ombi on Subdomain


I have my domain and I have made the A record for the subdomain and I want to point to ombi rather than or

I want to know how I add the subdomain to my box and for the box to be able to handle it point it to, at the moment I have it running though frame forwarding from my plesk site which works great but when some on tries to reset a password the /token link dose not work and pulls an error as it wont forward that bit on, I have it set to use the servers ip at the moment for resets etc just to get around that problem but this is not what I would like

Any help would be great as I have been banging my head with this for a few days now in and out of config files