One of things I wanted to look into in Substance Painter was adding a decals to my robot- especially on the Walkman device on his neck.
I found it actually not to be that hard of a process- starting with importing files into the scene to be useable of alphas. I then turned on the projection tool- dragging the alpha I needed into the material tab. I resized the alpha on top of the uv menu and then painted it in- creating the design I needed.
Decal Painting. (YouTube, 2017).