How did Kendall Jenner get rid of her acne? I would rather ask "did Kylie Jenner get rid of her acne?" instead.
If you look at photos of her up close and with no make up on, you'll see that her skin still has pimples and isn't flawless.
The only reason you might think Kylie Jenner's acne is gone is that photos of her are often photo-shopped (as they often are with most celebrities, so don't judge her).
Also she uses concealer and other makeup to cover her acne up. Not such a good idea since caking on makeup makes acne and pimples worse.
So really, Kendall Jenner has just been covering up her acne.
That doesn't mean there aren't ways to cover up your acne. She just hasn't discovered them/had time to use them yet.
But if you wanted to learn more about losing the acne on your face you could always do some research on: //beauty.blurtit.com/3946290/how-to-get-rid-of-acne-scars-fast