Although you might think that when you write a poem, it has to rhyme but it actually doesn't necessarily have to. Rhythm is just one of the characteristics of a poem. There are many characteristics of a poem, however, you don't need to include all of them.
Before you write, have a specific idea about what you are talking about and how you can express yourself in such a way that you create feelings in your reader. Write about something that you know well or have feelings for that you are willing to express on paper.
Poems are usually metaphorical. Make sure (if you can) to insert similes and metaphors in order to express yourself creatively and convey bigger ideas with less words.
*These are only one of the numerous basics of a poem
