Here are some approaches for writing poetry.
A couple of suggestions : 1) remember that poetry does not have to rhyme or have meter... Free verse works!
2) Chose a topic you have strong feelings about... it doesn't have to be serious feelings, it can be humor.
3) Take a piece of paper and jot down Words you think of when you think of that topic NOT sentences, just words.
Then you can organize those words into your poem.
You received good advice from GuruBlue. HEre's an example of using that advice:
Words to use--Barbie, cute, dresses, careers, fun
Poem from those words--
Barbie is fun
She is cute and wears neat dresses
Barbie shows me I can choose
I can choose a career
I can choose to have a fun career
I can choose to wear neat clothes, too.
This isn't a "good" poem, but it does fill the assignment parameters.
You can also take a word and make a poem from that. Example:
B is for the best she can be
A is for all the careers she does
R is for the really neat stuff she can do
B is for bringing me ideas
I is for what I can do now
E is for everything she has shown me.