I've done this before, you just have to do it really slowly. Make sure you paint is perfectly clean and dry, take off the backing sheet, lay a small corner piece on and then apply using something with a nice flat surface, like a credit card etc. Make sure you push the air out as you go, and the end there may be a couple of tiny air holes, get a pin and gently pop them, then slowly peel the top sheet off, again using the cridt card or what ever as you go, and presto it's on. Also a good move to rub over the decal with the card prior to fitment so it's stick properly to the top layer of paper, otherwise parts can end up staying on the bottom piece and totally f**king it up.
Best of luck mate