When you say 'switched on' I assume that you mean the ACD RTU is already on the CMS.
This link will take you to the Avaya document:
The outline of the steps are:
1) Add the IP address of the C-LAN board in the PBX to the /etc/hosts file in the CMS.
2) Turn off the CMS application (cmsadm\run cms).
3) Add ACD in the same menu.
4) Answer the questions as asked.
5) Turn the CMS application back on.
6) In the PBX add the CMS address to the node-name file.
7) Add the communication channel between the PBX & the CMS (change communication-interface processor-channels).
8) Verify that the CMS version is set correctly in the System Features form on the PBX.
9) Check the link status in the CMS. You should see an up tic (^) for the ACD that was added.
If any of the above steps makes you uncomfortable, hire a Business Partner. UNIX can be very unforgiving.
Kevin