As with most things bike related, making a vinyl sticker is marginally cheaper and takes far longer to do than paying a professional to do it. That being said, It gives you something bikey to do over winter and is quite meditative.
You're going to need:
* You won't need it if your design is one piece. This'll make more sense later.
^ Step 1. Tape an appropriately sized piece of your coloured vinyl to your cutting mat.
^ Step 2. Tape your template over the top.
^ Step 3. Start cutting. You'll need to be pretty firm to cut through the paper, vinyl and backing paper.
^ Step 4. When finished, remove the template and any counters.
^ Step 5. Ensure the pieces are loose then prepare a piece of transfer tape of an appropriate size.
The transfer paper will keep the spacing between the pieces of coloured vinyl. You won't need it if your template is once piece.
^ Step 5. Stick the transfer paper over the cut vinyl.
^ Step 6. Peel off the transfer paper, the coloured vinyl will stick to it. You can stick the backing back on the transfer paper to keep it tacky until it's ready to be applied.
^ Step 6. Peel the back off the transfer paper stick it down. You can move it around at this stage until you're happy with the position.
When ready, peel it back just enough to reveal the vinyl backing, but not so far as to ruin your previous positioning efforts.
Stick the transfer paper down once again, this time firmly pressing on it to stick down the vinyl pieces.
Finally, peel off the transfer paper carefully which should leave behind the vinyl.