Transferring patterns to clothing Help

It's easier in for instance Gimp (or Photoshop, or various other programs) - you need a program that can work with layers, layer masks, and also overlay settings. It condenses the work down to a few steps. Without those, you're looking at a lot of work. 

I usually work with a white version of the outfit I want to use as the linework/overlay. If I don't have one, I make one from the lightest version of the outfit I can find. Preferably use one without a design, but if there is one, pick one with the least intrusive design you can find that's possible to remove without it being visible - you can copy a part of the back to the front, or paint over the design, depending on what's easier. Also do hue/saturation to remove color so you're left with a white/light-grey outfit texture without any patterns or designs.

Then put the design you want under the overlay, mark the outlay (you REALLY need a program that can work with layers for this!), select the design, put a layer mask on it (this hides the parts I don't want to show).