私はKatherine(キャサリン)と言います。or 私の名前はKatherine(キャサリン）です。 In my humble opinion, 「私はKatherine (キャサリン) です。」is okay, but to be more specific, those two sentences would be recommended.

the topic particle is は. You got it right in the second example. But the first would have to be written as 私はKatherineです.