Arturia Keylab 61 mk3 - Pads in Ableton Live Midi device

Hi I habe a problem with Ableton Live Midi Mapping and Arturia Keylab 61. I want to make an individual Midi Mapping on a pad of Keylab. But i jumps back and makes a red square around something. What happened? How can i make individual mapping on special pads for example start a back track Song of a scene in Ableton or to turn off and on one sound in a scene of Ableton?