Find the subject. Who is doing something? Ricky. Ricky what? Ricky was. That is a complete sentence and it makes sense. Ricky going does not make sense. So, Ricky was. What does very unsteady describe? It describes how Ricky was. It describes the verb, making "very steady" an adverbial phrase. A prepositional phrase describes a noun. Nothing in this sentence describes Ricky. "Going" is a helping verb. Ricky was going. "Down the staircase backward," describes how Ricky was going, making it another adverbial phrase.
You didn't say what kind of phrase. I hope I helped.
Atticus was threatened and his children were treated poorly by their peers, because he had the courage to stand up for the oppressed. Harper Lee's main message to the readers is not to treat others according to who or what they are but according to their behaviours.
