"How I Got That Name: An Essay on Assimilation" is a title that tells us exactly what Chin's poem is about. It's a poem about how the speaker went from being "Mei Ling" to "Marilyn." The title's emphasis on names and naming is significant because it points to just how central names are in defining our identity.
We take our names for granted (probably because most of us don't even have a say in what we're called), but the story of our names is often a complicated one. Chin's title, then, points to the ambiguities and complexities that are inherent in names. Our names tell a story—and Marilyn's name tells us the story of her (and her family's) assimilation into America. "Assimilation," of course is the big word in the poem's subtitle, and it's the central idea—and conflict—of the entire poem.