To apply a vinyl decal, make sure the surface you're applying it to is completely clean and dry. Use alcohol to clean the area of all grease and dirt, then apply using a credit card as a burnisher.
Vinyl decals require a clean surface. Apply rubbing alcohol to a cloth or cotton ball, depending on the size of the area. Clean the area thoroughly until all grease and dirt are gone. Allow the area to dry completely. Next, run a credit card over the decal to make sure it doesn't stick to the backing paper. Pull the wax-like backing paper off of the decal, and stick it back on so that an inch of it sticks up above the decal. Now, place the decal on the desired location. Use the inch or so of backing paper to hold it in place. Flip the decal up, and start to slowly pull the transfer tape off. While you pull, use a burnisher to push the decal onto the application surface. Work from the top down and center out. Now, remove the clear transfer tape. If the decal is still stuck to it, it hasn't been applied hard enough. Use the burnisher to go back over the design and make sure it's applied correctly. Then, pull the transfer tape off completely.