Either find someone who know who to jump and ask them to show you or:
Find an easy tabletop (between 5 and 8 foot long with a fairly gentle kicker).
Find a place on the trail before the jump that you can comfortably roll toward the jump from. Roll up to the jump a couple of times to gauge what kind of speed you are getting. Just stay relaxed on the bike (central body position, knees and arms bent). If the bike feels like it is close to getting airborne add a couple of pedal strokes and try again.
Experiment with the speed you need to just get airborne without trying (just staying relaxed on the bike). Avoid pedalling too close to jump if you need room to get up more speed move a but further from the jump.
Once you are comfortable with this (practise lots!) you can think about “trying to jump”. The correct technique is to pump the bike into the face of the jump by pushing it away from you with you feet and hands (mainly feet). Don’t try and pull the bike up. If you try and pull the bike up you have a strong tendency to pull the bike to one side or twist the bars which can make for very sketchy landings (or a faceplant). If pushing the bike away from you seems like a weird idea practice on the flat pumping the bike with your feet (this is the basis of a manual too)
Once you are in the air keep you head up (don’t look at your front wheel) As you land, land the bike and absorb the impact with bent knees and elbows.
So get your speed right (don’t brake or pedal at the face of the jump)
Push the bike away from you not up
Keep your head up
Land the bike then land yourself