Tokyo, Toukyou
proper noun
The East Capital in Japan is Tokyo. If you look on a map and compare it to 京都 (Kyoto, the other capital in history), you'll see it's East of Kyoto, making it the East Capital, Tokyo.
とうきょう
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.
東京は大きい町です。
Tokyo is a big town.
私の会社から東京タワーは見えますよ。
You can see the Tokyo Tower from my office.
ハワイから東京に直行します。
I'm going straight from Hawaii to Tokyo.