First you need to make sure the surface you will be applying the sticker to is clean and dry, wipe the area with a solution of washing up liquid and water and thoroughly dry the area, then wipe with a microfiber cloth to remove any dust.
To apply a vinyl lettering sticker, remove it from the paper backing by peeling away the transfer tape. The tape will hold the individual pieces of your sticker design in place while you position it on your desired surface. Once your sticker is positioned correctly you can press the transfer tape onto a surface to adhere it. Next, use a credit card to apply pressure to the entire design to make sure it's fully adhered. Finally, slowly peel the transfer tape away at a 180 degree angle to leave the sticker adhered.
If your design is especially delicate, let it sit for 24 hours before removing the transfer tape. This gives your sticker time to adhere more strongly to the surface and makes it easier to remove the tape while leaving the design intact.