You do have to install an app on your watch in order to see the complication in the complication list. The complication list will give you the option of removing a complication while leaving the app on your watch. In the future this will be for the case that every app includes a complication but you don't want to scroll through 50 options on your watch if you know 20 will never be used. As it is now though, you have to install the app to get the complication option on your watch face.