Father, Dad, Papa
noun
This word begins with an honorific (お), making whatever comes after it more elevated. Then there's 父, which you know means father. Lastly, we have the honorific name ender さん. So this is a nice way to say father. You use it when you're talking to your own dad or talking about him with friends. You can also use this when you're talking about your friends' dads. In more formal settings, you'll want to use 父 (pronounced ちち) to talk about your own dad and お父様 to talk about someone else's dad. Don't worry, you'll learn that last kanji in a few lessons. Until then, it's pronounced, おとうさま.
おとうさん
The part you have to learn to read is the 父 portion. This uses the kun'yomi, which you didn't learn when doing the kanji. Imagine you are taking your venerable father to とうきょう. He's always wanted to go and this is the trip of a lifetime! Imagine walking through the streets of Tokyo with your Dad, taking in all the sights.
お父さんにメールした。
I emailed my dad.
お父さんはリンゴがすきです。
Dad likes apples.
お父さん、分かった？
Dad, did you understand?