The controls are very simple, the left and right arrow keys control the left and right movement. The Z key controls jumping. To attack monsters, most of them you need to jump on them. Some of them like the turtle are a bit different. With them, you need to jump on them, which puts them in their shell, but then you need to jump on the shell which fires it off, hitting any other enemies (Or you!) as it whizzes off.

You can jump up at the yellow coloured boxes which releases coins, and sometimes releases upgrades such as making you larger, giving you temporary invincibility etc. Now, go save that princess.