Nothing too tricky's going on here—the title of this poem just gives us some basic information. Essentially, it tells us that this poem is a prologue, a short piece of writing that is meant to introduce a longer work. In this case, that longer work is a book of Bradstreet's poems that was sent to the publishers in London without her knowing about it. The book itself, which appeared in 1650, was titled The Tenth Muse Lately Sprung up in America.
What this does, as a prologue, is to confront the issue of gender right away. It gets out ahead of the potential criticism, which is a pretty great strategy for dealing with the flak a female writer might expect to get in Bradstreet's era (hint: lots). We think it also sets the reader's expectations a little low. The speaker sounds so modest, sometimes even a little short on self-esteem. But the work that this introduces, The Tenth Muse, is a pretty serious, smart and carefully crafted book of poems. No matter who you are or when you're writing, it's not bad to have your readers going in expecting too little, rather than too much. The title of the poem locates that message front and center for any male readers who might have their noses put out by Bradstreet's writing.