Make sure surface is clean & dry.
Position the decal on the wall using masking tape to hold in place
apply the tape along the top & use as a hinge.
Remove the sticker away from the backing paper very slowly if any of the sticker
does not come away apply pressure on the front of the carrier paper with something firm
like a credit card
Once the backing paper has been peeled away apply the sticker to the wall &
apply pressure using something firm like a credit card starting from the
middle working your way out
Peel the carrier paper away very slowly if any of the letters lift apply pressure
on the front face & try again
Stand back & admire
If you are still unsure watch the you tube video below