Firstly you obviously need your poem. Then you need a melody/tune that you want to fit your poem into.
Make up a simple melody, maybe just 3 chords repeated, with a 4th one thrown in here and there. (Minstrels in history told stories to just a few notes).
Fit your poem (lyrics) into the tune.
If it doesn't fit perfectly, repeat a word, or a few words, or even a full sentence. Or drop a pause in.
A chorus could simple be the title of the poem, or the last line(s) of a verse repeated.