When writing a poetry explication you will want to analyze the basic elements of the poem such as plot, form, imagery, and literary devices.
This poem was originally written in Spanish, and that is important to note. The citation for the version I used is at the end of this answer. Translations differ, but the basic meaning and form seems to be the same. Language usage is also largely the translator’s choice, so I will focus more on images.
The poem is formed from 3 stanzas, each centering on a metaphor. A metaphor is an idea that is related to a topic. All of the metaphors compare the daughter to something she is not. Each stanza is also three to four sentences following the same pattern (and this is the same in the Spanish original). The pattern is two “I don’t want” sentence sandwiching or framing the reason why, and reinforcing the idea that the speaker wants to spend time with her daughter.
The metaphors couch real fears in fanciful language. For example, in the second stanza the speaker is afraid her daughter will “get made into a princess.”
If she wears golden slippers
how can she play in the fields?
And when the night comes should wouldn’t lay beside me. (stanza 2)
This colorful metaphor describes a real fear, that her daughter will become too good for her and she will lose the closeness she feels with her.
Now you can focus on other images in the poem and explicate them too.
Mistral, Gabriela. Selected Poems of Gabriela Mistral. Albuquerque: University of New Mexico, 2003.