In English you only have the verb to be but in Spanish we use two different verbs ser and estar
To fully understand the uses of the verbs ser and estar you should read What are the differences between "ser" and "estar"? When to use each?
Regarding you question... First, the question could be ¿Cómo es usted? or could be ¿Cómo está usted? and those are two different questions.
The first asks about you as a being (permanent state) and the second asks about your current state (that could be temporary or transitory)
To the first question you could answer Yo soy bueno since you are a good person. The question uses the verb "ser" (¿Cómo es usted?) so you answer with the same verb.
To the question ¿Cómo está usted? that uses the verb "estar" you should answer with the same verb Yo estoy bien since at the present time you are good/ok/fine.
The above has to do with the meaning of the sentences and the differences between ser and estar but also notice that the use of fine in English has some differences to the uses of good and ok so I'll give some valid translations (that may confuse you more but anyway...)
I'm good = Estoy bien / Soy bueno
I'm fine = Estoy bien
I'm ok = Estoy bien.
He is ok = El es buena gente
He is a fine guy = El es una persona bueno/correcta
She's fine = Ella está bien / Ella es bonita
I'll think of more examples and continue writing