HOW DO I NOT USE ALPHA IN ART AND WHAT IS ALPHA?
alpha is a pixel's opacity, the 4 channel in a rgba (A is alpha) image, you cannot use it by using jpeg images or just not connecting the alpha channel. it really depends on what game engine you are using; it will be slightly different for everyone.
read this for more detail "Alpha compositing - Wikipedia"
you probably did not use it though, if there are any tones that are not that are not your two main colors then you did