Position the crank with the key slot at 12 o'clock (as seen from bottom) and the front main bearing up with the rod arms forward as above at the rear of the engine.

Pick the crank up and move it slightly forward while guiding the bottom rod arm into the right hole of the case. You can reach through the right hole if need be.

Now move the upper rod arm through the left hole and tilt the crank forward...

...as you do this grasp the flywheel crank end and slowly turn the crank CCW a small turn to get the rod arms spreading out the holes.

View of the right side...

...view of the left.

Continue lowering the front of the crank while turning CCW slowly.

The crank is now resting in the engine case.

Right view...

...left view with the front bearing plainly visible.

A view of the front with the crank ready to be pressed home using the rear main bearing plate.