Do you mean how to use boards running contiki with Ci40, or running Contiki on Ci40? If it's the former:
The answer to this depends on what you're trying to achieve. If you simply want to send data from a node device to Ci40 you can do this over WiFi by connecting the node to the Ci40 SoftAP network. If the board has 6LoWPAN you can follow this guide to use UDP.
If you want to manage the Clicker board as a device in the same way Ci40 is managed (using AwaLWM2M, Device Server and Developer Console) then the process is more difficult. We are planning to release a workshop on the docs site to explain this - I'm working on that now.