Treating plywood is required when you are placing it in an area that is exposed to the elements. Since the material is exposed protecting it will extend the life expectancy. The process requires only a few items purchased at your home store and can be accomplished by any homeowner. It's important to allow yourself a couple of days for the product to dry and cure.
Dip the foam paintbrush into the sealer.
Apply the sealer to the plywood. Make sure you are going with the grain of the wood. This will be a bit tricky since it may shift, but just follow the grain.
Allow the sealant to dry for 24 hours. Sand the plywood to scuff the surface of the sealant. Wipe off the dust with a damp cloth. Apply another coat of sealant