Well technically all you need to do is once you have the textuer made, you create a new material. THen in the color region click the checkered box. Now you select file, then you use the file that you want for it. It may cause problems because all you did was project a region of your vac. You may want to project the entire section and move the UV's around to give the area you want more area, if theres nothing else that you need to have show up on the vac, cuz if you use the second technique, the rest of the texture will stretch.