Parentheses work like an aside in a sentence or, as I like to think of it, a whisper. When you read a sentence and you come across a parentheses you feel like the author is almost whispering in your ear and saying, 'Here's a little bit of extra information.' It's not vital that you know it but it's interesting. You can punctuate parentheses two different ways. You can tuck then inside of a sentence if it's a partial thought, or you can make a parentheses it's own complete sentence, if it's a complete thought. I'll show you how to do it.
So in this sentence I might say to my mom, over the holidays, 'I bought a gift for you (and two for me). In this case 'and two for me' is part of the sentence and so I tuck it in. I say,' I bought a gift for you (and two for me). Whenever you're tucking the parenthesis inside of a sentence you want to put the end punctuation outside of the parentheses. Now what if I want to use the parentheses in a complete sentence, for it's own sentence, as standalone sentence if you will. Well, it would look like this. 'I bought a purse for you. And I might say, in parentheses, (I bought two dresses for myself.) So in this case note that we open the parentheses, we capitalize the first word, and we tuck the end punctuation inside of the parenthesis before we close it. I hope this gives you some ideas about how to use the parentheses.