Although every teacher may have a different set of instructions for writing a paragraph about symbolism, here's a general method you can use.
Step 1: Find a symbol that you like.
Look for an object that gets mentioned more than once, one that the characters pay attention to.
Some options for Inside Out & Back Again include Hà's papaya tree, her mother's amethyst ring, the photograph of the father, the baby chick that Hà's brother clings to, or even her nightgown that Hà unwittingly wears as a dress during the day.
Step 2: Write a few sentences to explain what your object is and how it plays a role in the story.
Tell what it is, what it looks like, and what the characters do with it, or what they say about it, or what they think about it. You may want to use some short quotes from the text of the story to help show exactly what you mean.
Let's do this for the papaya tree:
Back at home in Saigon, Hà is thrilled when her own little papaya tree starts to bear fruit. That papaya is her favorite thing to eat, and she adores the tree itself. Hà compares the fruit it grows to a "fist" and a "light bulb," and she plans to give the first fruit to her mother, whom she loves dearly. But when Hà and her family have to escape the country, and they end up in Alabama, Hà misses her tree and thinks of it often. She thinks of eating papaya when she has to deal with the vastly different and, to her, disgusting American food. The only time she even gets to eat something resembling a papaya is when someone gives her those gross, dried-out, sugary strips of it. She longs for her tree.
Step 3: Write a few sentences to explain how your object seems to represent one or more bigger ideas. In other words, what kind of feeling or quality or desire or struggle or does the item stand for? Be sure to tell why or how you came up with your ideas.
When it comes to saying what something represents in a story, there aren't always right or wrong answers. But there are definitely well-supported answers and poorly-supported answers!
Again, let's do this for the papaya tree:
Because Hà associates her precious papaya tree with her homeland, and because a tree is rooted into the ground, I believe the papaya tree represents for Hà all the comforts of home and the feeling of belonging somewhere. When Hà misses her tree, she's also missing her entire life back in Saigon, and she's missing her "roots"--her sense of belonging to a place and thriving there. It's important that Hà's homesickness begins to ease and that she begins to establish a better sense of belonging only when she finds comfort in the reconstituted, de-sugared lumps of the previously desiccated papaya fruit.