It is easy enough to find the four positions for the lift arms with the engine off. Raise, neutral, lower, float.
No difference with engine running except you get to watch the lift arms fall.
Raise the lift arms high, and shove the stick fwd and it should lock in a detent, and the lift arms wil descend to the ground and float as you drive.
If you have a load in the bucket, you might not want to be playing with the float and suddenly pull the stick out of float. The arms will lock and may raise the rear of the tractor with a heavy load, and you might generate a hyd spike that could damage things.