I don't think that is the original inverter, but in any case, use a multimeter to verify which of the leads from your solar panel
is positive and which is negative. You can connect the solar
panel to the controller then, from the controller to the battery
terminals or to the connectors in the fuse area. It looks like they are using the top, black as positive and the bottom white as negative, but trace the wires to the battery to confirm.
Standard coding for DC is red for positive (+) and black for negative (-).
Probably the ring terminals go to the battery and the plug, which you'll need to cut off, goes to the solar
panel. The controller may be marked to identify which is input and which is output.