Something like this should work:
In 1, put the contract address. In 2, put the contract ABI. Once the ethereumcall module is connected up to a getcontractat module, it should display a number of functions that can be executed. Use 3 as an easy way to trigger the ethereumcall manually (in this case, owner is a driving input in the ethereumcall module, meaning it's waiting for something to flow into that input before the module runs, by clicking send, that makes a value flow into it - driving inputs can be changed by hovering over the inputs).
Make sure a valid ethereum account is set up in ethaccount (I think only testnet - rinkeby or ropsten - interactions are currently enabled in this particular module, but a streamr dev would need to confirm).
Make sure the canvas is set to running before trialing. If successful, the returned value should be displayed in the table.
hopefully that's gives enough detail, just ask if you have any more questions.