The poem conveys the idea of freedom. The main idea is stated at the beginning of the poem when the author says I have a dream and it is to be free as a bird.
The author doesn't use many devices since the poem is really like a narration of the author's desires. It has neither metric nor rhyme.
The poem shoes that the writer is a teenager that is under supervision of his or her parents.
When the author says: Imagine myself choosing what do do. It means that the author is told what to do.