(i don't know if normal users can post tutorials here,but here we are)
I'll teach you all how to do a pixel adoptable using MS Paint! We know,we know...that's a very simple software,but you can do awesome stuff with it. Who said you can't?
It's very easy. Well...maybe not,but it's very fun!
(also sorry for Portuguese Brazilian,that's my language)
Make a new image and resize it to 170px X 220px. As we know,that's the only image size Maxicanvas accept.
Now,if you have the right size,you can now draw! But first,make an sketch. (i used orange color because why not?)
Trace the sketch,using curve/line tool and shapes,if necessary. (i'm using black line)
Now it's time to color! Use any color you want,and fill with bucket tool.
I hope i helped you :3