GIMP is a decent Photoshop clone that's free. I've seen some pretty amazing things done with it if you want to try that. But this is cute. :3

Thank you! I shall try......maybe a link to it? C:

Don't have a link to it, but you can Google it and it'll be easy to find.

I have no idea how to use layers..

Layers are like tracing paper, essentially. You can, for instance, put your outlines on one layer and then paint all the colors underneath it. The benefit to them is that if you mess up a color on the layer that's below the outlines, you don't have to redo the outlines because of one mistake. They're really handy to work with. I encourage you to take a moment or two each day and learn how to use them to benefit you. :) They are absolute life savers.

I shall try! Thank you! but how should they go? like should i leave the background layer for the color?

It's entirely up to you. I usually leave the background layer separate from the color layers so that I can easily delete the colors and not have to muck around with stuff I can't delete.