Hi,
You can drag and drop the sprite renderer component to where you place the actions, and it will create a get/set property action, where you can configure what you want to get ort set. To do this most easily, mind the lock functionality in both the inspector as well as the FSM.
Alternative, you can create an object variable type (in variable pane), and then set object type: navigate the drop down lists (press U a few times and find Unity Engine, and then in the submenu, press S a few times to find sprite) and you should have what you need.
Finally, take a look at Linker Wizard (tutorials on YouTube, tool in Playmaker menu).
Cheers,