Where is the grid inputs window that should have grid price, sell back rate etc?

Click the Add/Remove button at the top of the schematic, and look for the Grid section in the bottom left corner of that window.  Choose the radio button that says “System is connected to grid”.  Once you close the Add/Remove window, the Grid button will appear in the schematic diagram.  That button gives access to the grid price, sellback rate, and so on.