Guide on adding a new model, animation, and creature to HoMMV

Here, here is my manual on creating icons in Photoshop!

Does anyone have a working link to a manual on creating icons?
I tried using Photoshop with a plugin to edit existing icons in dds format, but the result was a mess with a black background and a changed color, even though I only mirrored the head rotation so that it faces from right to left. I don't understand what I'm doing wrong