Terra cotta pots are porous pots made from clay. When using the pots outdoors, it is important to coat them with a protective sealant to keep out water and protect the clay from the elements. You will need to coat both the inside and the outside of the pot with the sealant, even if you paint it first.
Dampen a clean cloth with water and wipe down the inside and outside of the pot to remove any dust or grime. Let the pot air dry for two hours.
Paint the inside of the pot with a coating of exterior varnish, using a foam paint brush. Let the varnish dry according to the directions on the package. If you want to paint the outside of the pot before sealing it, use an acrylic paint and apply it with another foam paintbrush.
Coat the outside of the terra cotta pot with a layer of exterior varnish. Let the varnish dry according to the package directions, then apply one more coat. Let that coat dry before you move the pot outside.