Open Fuel cock - use the mapped key/button or click in the lever, right side of compass.
Leave throttle lever between 0 ~10%. In fact can be more, 0 to <30%, but more than 10% the plane will start shake.
Press the "magical" key "E". They forget to model the start button.
Await temps raise for above ~60, open water radiator and go.
Magnetos switches is just
"what if", in CloD has no practical effect, if you switch then ON the "magical" key E move switch OFF and then ON, so useless set then... Well switch magnetos serves for make YT videos "Spifire Startup".