Brush some water on the decal surface (the side with the color) OR dampen the clay surface wet. 

Place it on the flat surface of either leather hard or bisque-fired clay surface, (curved surfaces can create folds)

Use a dry hake brush to drive out the air in between the paper and clay surface. Wait until the paper nearly  dried and peel it off from the work.

Apply any clear glaze on the top. Fire to whatever needed. The firing temperature can be from cone 06 up to cone 10!