Good poetry starts with feelings. Start by logically deducing which feeling your poem is about. Then elicit that [passion | intensity | warmth | ardour | fervour | vehemence | fire | excitement] in yourself and use it to inform your choice of language.
... intimate connection between language and emotions is a must for
contemporary poetry where everything is designed to act directly upon
you: a poet’s word choices aim to trigger your memories, associations,
and images, their tone, meter, and rhythm reach for your body, while
their rhymes, repetition, and alliteration land on your tongue to be
tasted and savored.
(Aneta Pavlenko, on Psychology Today)
You're a prose writer and so you already have a good vocabulary so all you need to do is connect to your primal emotions. Once you're there, you can use them to inform your poetry.
Here's how to get to your feelings:
Every now and again I find myself welling up at a certain point in a movie (at which point I blink furiously before the wife notices). What you (and probably me) should be doing at that point is writing a poem. Get down in words what's moving through your body; because this is where the emotions live. Record what's going on in your throat, heart, chest, skin, eyes and mouth and then use it.
Fire up a browser and search for pictures of people who are experiencing emotion. Then mirror those expressions and postures in your face and body. It might sound like a weird thing to do, but it works. Paul Ekman did some experiments in this field that reveal that we can trigger emotions by artificially putting those expression on our face.
Sharing how you feel with a trusted friend (or an anonymous forum) is a great way to bring your emotions to the fore. Practice revealing your love, anger, disappointment, shame, embarrassment, guilt, and pride with others and you will find that you can access those things more easily when it comes to writing poetry.
Sometime we try to repress our emotions (like I do when watching movies) or rationalise them away by telling ourselves that they don't have a purpose or that they aren't useful. When we do this, we find that when it comes to writing poetry we view our words as 'cringe-worthy manure'. Learn to love and accept emotions and the language they inspire.
I know that this answer probably seems like it's about emotions rather than writing, but there is a connection. Even if it doesn't seem to make logical sense, it's something worth trying. And if it works, then you have another tool in your box as a writer, especially if you have a need for poetry (or well rounded characters). There are, of course, other ways, but this works for me.