Here you go.
As you can see, I have some pretty good speed going towards the stairs. You may want to start at a regular pace for now until you are used to it, but latter, on the extra speed will be used for more momentum to get up and over whatever your trying to jump.
One noticeable thing is the compression of my tire. I almost bottom out before I launch off. I always end up getting my compression when my pedals ares around 12 and 6 o’ clock position, maybe around 1 and 7. At the same time, my whole body has compressed down just a little bit. You may want to let some air out of your tire to get this compression.
As my pedals get to a more horizontal position, I spring up. You can watch my whole body go straight, my free arm swing up, and the compression of the tire always helps. Im almost leaning forward a little, but not by much. And I am really pulling on my handle.
As soon as I have passed the 2nd stair, you can see my legs bringing up the uni.
By the third stair I have pulled the uni even more in front of me. My free arm is still out.
BY the 4th stair I am in a position very familiar to this > . Top half is folded way over, This movement gives you momentum to get up and oer higher object, on lower object this wont be need. You can also tell how folded up I am, getting the tire as high and out as I can to get it onto the top of the stairs.
I land, body straightens up, I pedal forward and land my hop.
For you, start with curbs, one stair, or one pallet. Find your jumping position, I go left foot forwards, others go with their right. Get on your uni and ride to the spot where you want to jump at. Probably just a few inches away from the ledge. Hop in this one spot and turn yourself around so you are facing away form the ledge. Ride straight out now a fair distance, and once your back in your jumping position, hop there a few times to remember that spot, and mark it somehow.
Now you have a perfect run up to your object. Mount on this spot, hop a few times if you need to to make sure your there, ride at your ledge, and jump.
Practice the curbs or small ledge till its natural and something you can do with your eyes closed. Now try 2 stairs, or two pallets, practice those until they feel like curbs and are easy. Keep practicing, keep pushing yourself. Don’t worry if you get stuck trying to get up something, jsut find something a inch or two smaller.
Hope this all makes sense and helps with your jumping.