Assuming you have the basics of jumping down already and hit all the smaller jumps first, the key thing with bigger jumps is to watch other people hit it and pay attention to their drop in spot + line.
A big jump is exactly the same as a smaller jump, except getting the speed right becomes even more crucial because knuckles and overshoots hurt way more (especially knuckles).
You should be watching other people hit the jump first and noting their drop in spot, their line, how much speed checks they do, whether they scrub speed off by spinning too early off the lip etc. etc. while seeing where they land.
If they overshoot take note, if they undershoot, also take note.
You want to know exactly where to drop in and what the perfect line into the jump is BEFORE you hit the jump so you get the right speed.
If you need to, do a test run of your line first and pull out before you fly off the jump, this can give you an idea of what the line feels like and also give you a feeling of whether it's fast enough or not.
Besides this, the fundamentals of a bigger jump are the same that you use for a smaller jump, just remember to ease into it and don't rush it.
If you feel you have the speed wrong, pull out of the run in and abort the attempt, don't try to forge ahead with the wrong speed. It's better to wait until the next run then to get the wrong speed on a jump and blow your ACL up.