Combination of pulling on the bars, leaning back and pushing on a pedal. Higher bars make it way easier. Get out on some grass and practice lots. If you've got brakes keep a trigger finger on the rear brake to keep from looping out.

Dude in that video is sitting just barely in front of the rear axle so he's almost at the balance point already, so very minute shift back of the shoulders and light blip on the pedal and he's up.

One thing I've never gotten down is manuals. I gotta pedal all the while my front wheel's in the air.

Here's more video for inspiration: they got squishy forks, so use that - compress suspension, then pull up, lean back and pedal.