Use the on-screen buttons to move. Grab a green arrow power-up to get the jump power, then jump into the finish portal. Later levels have more power-ups to find.
Use A and D or Left and Right to walk. Grab a green arrow power-up to get the jump power, then press W or UP to jump. The more green arrows you get, the higher you can jump!
In later levels you'll also find power-ups to push crates and run faster. Get them all to reach the finish!