Just click and drag somewhere in this white space below, and you will begin to paint, if you scroll down, you will find your artists pallet and further instructions.
I’m sure you will work it out, there are buttons for zoom, panning and if you click again on the selected pallet colour it will randomly change to a new colour. You can’t save your drawings but you can print screen them. On windows there will be a button on your keyboard called “prt sc”, once you press this button you can paste the screen shot into paint or any other graphics software and save it.
iPhones and MAC’s also have a similar feature but they save the screen shot straight to file here is how you do it:
MAC: Command (⌘)-Shift-4
iPhone/iPad: Press Home+Sleep at the same time.