"watashi wa" is indeed used as "i am" with "watashi" = "i".
"wa" is a kind of article that japanese use to tell you if something is a subject, a direct object, indirect object, etc...
you would also hear words like "anata o" and "anata wa". with "anata" meaning "you".
japanese also have endings that would tell you if is in the negative like "wakarimasu" and "wakarimasen" or if it is a question "wakarimasu ka?".
i'm not very good at japanese but i can still remember much of what i learned several years ago.