The promising possibilities offered by supernumerary robotic wearable arms are limited by the lack of an intuitive and robust user interface to control them. Here, utilizing admittance control, we propose a ’Collaborative limbs’, or ’Co-limbs’ user interface for wearable robot arms. The key feature of this user interface is its intuitiveness enabling even first time users to immediately move and use the, normally stiff, robot arms for assistive tasks and even teach the robot simple and useful movements. We demonstrate the diverse range of applications enabled by this simple but powerful user interface through example demonstrations in the Passive Assist, Power Assist and Playback modes.