Clean the surface!
The cleaner you get it the better it’ll stick and make sure it’s dry if you used something wet.
Rub it, cutely or lewdly.
Just make sure that it’s stuck to the clear side (for kiss cuts) so that you can apply it where you want. Peeling it back somewhat perpendicular seems to work the best.
Take your time and line it up perfectly and move from one side to the other. Generally go from top to bottom especially for larger ones.
Rub something hard over it.
Get a straight edge and run it over, starting from the middle, pushing out any potential air bubbles. The less air bubbles, the stronger the stick.
Remove the transfer tape!
It does take some force so just pull directly down or up, slowly.
And you're done! You can rub her over once more just in case.
Other things to consider
Use common sense! Whilst they are rated for outdoor use, don’t place them anywhere there will be extreme temperatures, take care of your girls.
Don’t put them anywhere normal stickers wont go, that is on surfaces which aren’t flat and smooth.
Take care when cleaning the surface afterwards, sharp points and corners could get lifted accidentally.