It's either going to be configured as a SIP Device or SIP Trunk.
If the device is supposed to REGISTER, then configure it as a SIP Device under Device->Phone->Add New
If it is a SIP Phone, make sure the DN configured on the device is the same configured as in CUCM.
If the device is going to send calls to CUCM without REGISTER, configure it as a trunk under Device->Trunk->Add New
If it is a trunk and you want to be able to place calls to it, then configure a Route Pattern to point to the trunk under Call Routing->Route/Hunt->Route Pattern.
Check the CallManager Admin guide for your version for information on how to configure each.
http://www.cisco.com/en/US/partner/products/sw/voicesw/ps556/prod_maintenance_guides_list.html
HTH