It's under the application's preferences, needs to be launched as administrator to set it. It's also packed in the registry but that's not a great place to play with it.
Otherwise it is set in the UCM under the phone's settings, search by directory number using a number on the CIPC client if you don't know the device name you're looking for.
You can specify a name that's not the actual adapter name but this does break call monitoring/recording solutions with the contact center amongst other things but it will work as a phone.
