To use the payload from a message in a logic on your Streamsheet you need to link the Inbox payload to cells on your grid.
This is done over the READ() function.
With this function you can reference certain payload structures to a cell. This will than update with every new recieved message. You can either type in the whole function, or simply drag and drop the payload you need on the grid.
Now you can go ahead a implement some logics …