Summarize:

Copper leaf sheets come in booklets and are separated from one another by protective tissue paper. Expose your first sheet of copper leaf and carefully lay it onto the sized surface. It will stick immediately. Gently pull the booklet away and let the rest of the sheet fall flat onto the surface. Press down firmly to adhere the copper leaf.  Wear cotton gloves so the copper leaf doesn't stick to your fingers. Work in a draft-free area. Copper leaf is extremely thin and can be easily disturbed by a draft. Use your fingers to tap down the copper leaf to ensure it is fully adhered to the surface. Then use a soft paint brush or cotton ball to brush away any excess leaf. Continue the same process of exposing the sheet, dropping it, tapping it down and brushing away the excess until you’ve covered the whole surface. Once you've covered the entire surface of your project with copper leaf, inspect it closely. Holidays are places where the copper leaf didn’t adhere properly. Use more copper leaf to fill these "holiday" areas in. Try to avoid touching the gilded surface too much at this point, since your fingerprints can leave permanent marks on the surface of unvarnished copper leaf. Surfaces gilded with copper leaf will tarnish easily and quickly. A protective sealer needs to be applied to protect from oxidation. Apply one coat of oil-based varnish or specially formulated acrylic topcoat with a paint brush. Allow the sealant to dry completely before handling your project.  See the instructions provided with your varnish product for more information about curing times. You can obtain varnish or topcoat from most home improvement and craft stores.  It also comes in spray formulas.
Fold back the tissue paper to expose the copper leaf. Remove the excess leaf. Look for and fix “holidays” on the surface. Seal and protect the surface.