How to use choke

[Lims]

I just got my first dirt bike. I’m not sure how to properly use the choke. Is it supposed to be on, off or inthe middle when i start it?
Once it starts, then what-on, off, or middle?

Crf125 big wheel.

 

[Okiewan]

pull it all the way out to start, let it run for a little then push it all the way in.