Up until the day you intend to use them, keep your decals rolled up in their shipping package.

You must wait for the paint to cure if you intend to paint the wall or if you have already done so.
Allow the paint to dry for a minimum of two weeks before installing decals.

It is crucial that the surface you intend to use is flat, clean, and dry.
Grab a moist, lint-free cloth and wipe down the surface before you begin.
Be sure the surface is completely dry before beginning the installation.