Do progression exercises.
Do squats while riding at speed, to get accustomed to bending knees and keeping your board straight.
Start doing small pops in flat areas while riding at speed to get confident about landing at speed. Use your knees, not shoulders to pop.
Once you get comfy with those, try poping off a roller at speed to catch some air.
Escalate to small side hits and small kickers.
Always keep your whole body paralel with the board, when you pop. Commit to jumps, don't try to bleed off speed at the last possible second. Condition your mind to go straight 2-3 meters before the roller, and 2-3 meters after the landing.
With a stiff board like that it should feel pretty stable and a whole lot of fun.