Feral Heart

My sister wanted me to turn some images into objects that she can use as posters to put in one of her maps. I don't know how to do that, so I was wondering if someone could help me. I have blender and I know how to make a plane, I just don't know how to make the material/texture of that plane the image I want it to be, or how to convert the final file to a format that FeralHeart can read. Does anyone know how I could do this?