You need to create a multi-instrument. This is best done from the Environment's Audio layer.

1. New Menu>Multi-Instrument

2. Connect this multi object to your Instrument track where you want to plug-in Kontakt.

3. rename this multi Kontakt 2 and click (activate) as many channels as you need. This enables those channels.

4. Select the Instrument track in the Audio layer and in the properties window set the MIDI channel to "ALL"

5. In the Arrange page, click hold the track name and then select the Kontakt channel 1 object from the Audio list.

This will be assigned to Channel 1.

Do this for all extra MIDI channels.

Please note that as a plug-in Kontakt is limited to 16 channels, as specified by the MIDI standard.