Oh boy. That'd be a real fight even if you knew exactly how to get to it.
To lift the boom, you can open the hydraulic lines (both ends). Or, in your situation, we usually had someone in the seat, go through the start procedure to get the hydraulic lockouts released and they hold the left pedal back for boom lift. And then another loader lifts the boom and then they lock out the boom when high enough. You have to (should) put a large block under the rear because the loader with rare back on rear axle before boom raises. Of course, none of this helps if you don't have another loader.
Not sure what to do in your situation. No neighbors with a loader of any type? Tee in to the hydraulic lines with another hydraulic source (tractor?)???