I can't quite tell from the angle of that picture. Is there a plug or a hose on the outlet of that valve.
The black lever looks like the front wheel drive engagement lever. The red lever is the high/low range lever. There should be another on the same side, higher up, beside the seat, that controls the fluid flow to that diverter valve. When the diverter valve is turned one way (clockwise, IIRC) then the lever controls the 3ph height. When the valve is turned the other way, the lever sends or relieves fluid from whatever is piped to that outlet. If your FEL is fed through that valve, then the 3ph lever must be locked up to operate the FEL.
If you haven't already,
download this manual and look at page 295 for a more detailed description.
The preferred way to power the FEL from the tractor's hydraulic system is to use the hydraulic block. See page 302 for that info.
And of course, as Wolfman already mentioned, many small tractors use a separate hydraulic pump driven off the front of the engine (or possibly even the PTO). However, I can see a hydraulic return line in one of your pictures, so I don't think that is so in your case. Separate pumps usually have separate reservoirs.