I play in VR and there are 2 little levers left and right of the ignition lever. Turn them to positions 7 and 5 o'clock. Before they are at 8 and 4. Pull ignition. Press the start buttons. Up and running!
Here's a great Goose manuel:
https://krepelka.com/fsweb/learningcenter/aircraft/flightnotesgrummangooseg21a.htm#climb