"watashi wa" as you might already know, means "I". But the particle "wa" (the second "wa" in "watashi wa") is always written with "は" . The hiragana "は" is usually pronounced as "ha" but if は is used as a particle, it is pronounced "wa"
e.g.
わたし は きょう は はやおき しました。
(watashi wa kyou wa hayaoki shimashita)
I got up early today.