Decals: Creating your own [Tips]

[Numerius]

I tried it, but no success. I think I'm doing something wrong - either creating the decal wrongly or using a wrong tool.
To create it I'm using the material editor with "decal", "default" physics material, "Alpha" blend mode, and a check on Diffuse under Texture units.
It started out as an experiment, but now I really want those decals in the level, but I could not find a tutorial on how to create it.
Uh. I must be missing something.