When a complete, independent sentence is entirely enclosed by parentheses, the period goes inside the closing parenthesis.
- Charlie scarfed up every Cheeto that fell out of the bag. (I wasn’t fast enough to stop him.) At least we won’t have to sweep the floor.
But, if the parenthetical material is nested inside another sentence, the period should go on the outside.
- Charlie barked wildly when he caught the scent of fresh bacon (his favorite).