Generally with a 2 speed rear, when empty or loaded light, you can just drive it like a regular 5 speed, and when heavy, you can split each of the gears. Really heavy, start 1st and low rev up, split to high , usually rev up, tap the throttle a bit than back off and it will idle back then hit the gas again and will catch the split, some need the clutch.Wind out 1st high, shift to 2nd and split to low while shifting. It get's pretty natural after a while.
With not too heavy loads you can usually grab 1 and 2 , then split 3 4 and 5, going downhill, no splitting needed.
You'll likely jerk and buck the thing a bunch getting the hang of it, thankfully the things are pretty sturdy and you shouldn't hurt anything.
Enjoy the new toy----------Robert