Wish i could be more helpful, but since I cant try anything right now i would suggest you figure out how to get such a decal placed in your level without worrying about blueprints or coding, creating, moving, or destroying it dynamically. just add it as a decoration. once you figure out how to do that, You can probably get the same results by either spawning it in blueprint or having it already exist as a component where you toggle visibility on/off and initialize it with the same settings that worked when t was a fixture in your level. from there you can figure out how to aim it.
Decals are kind of like tv projectors, casting an image from a source point onto a surface.
hope that helps if only a little bit.