I cant get a image of the shirt onto a decal, any help?

So i've been scripting for awhile now but for some reason I can't get past this simple step and it's killing me. I'm making a gui where you click on the image of clothing to buy it, but when I try to put in the ID of the shirt onto the decal, it shows the template, not the shirt. Solutions/tips? I feel like the answer is right in front of me but I cant see it