UCCX refers to the CTI Ports as a "Unified CM Telephony Call Control Group". It is accessed from CCX Administration > Subsystems > Unified CM Telephony.
The CTI Ports are assigned a Calling Search Space (CSS) through CCX Administration as a group. This works like any other UCM CSS: the partitions in this CSS dictate what calling abilities CCX has. You may need to click the "more" button on the call control group to see the CSS dropdown option.