Not just ramp size but also speed, and lots of it.
Spot your ramp, it should be down wind of you, not out in front, bear off, gaining speed in the process, heading for that ramp. Hit the ramp, but at the same time turn back upwind, but not too much, you want the wind to hit the bottom of your board. As soon as you leave the water, pull your knees up and sheet in the sail at the same time, it's called "putting on the squeeze", and hold that position, you are now a wing. That will give you more lift and also more distance, what we call "travel air", hold it until you start heading back down, then straighten out your legs as the board meets the water, giving you the shock absorption needed for a soft landing. Always land either nose or tail first, never land the board flat, your board will hate you for that.
Flat landings can kill off a board pretty quickly.
For a nose first landing, hold the squeeze all the way until the nose hit the water first, it should happen naturally if you are putting on the squeeze properly.
For a tail landing, come out of the squeeze earlier.
Nose landings are scarier and a bit more advanced, but you come out of those very smoothly and still with some speed.
Tail landings are easier but you'll scrub off almost all your speed in the process.
Try to land pointing off the wind a bit, easier to get going again w/o rounding up and having to water start all over again.
That's the short version.
Below is a pic of putting on the squeeze, board up, sail down, he's heading for some distance.