Handle downlink messages for nrf9160

Hi. I am currently evaluating nrf9160 on a Thingy 91 board and have the environment for the asset_tracker application up and running. 

I want to be able to handle JSON messages sent _from_ the cloud (using the NRF cloud portal to start with) but I can't find any examples of this. Do you know where I can find an example or guide for this? Thanks in advance!