the sestina is a 39-line poetic form. six end-words (teleutons) are repeated in a given pattern for six stanzas, and then the poem is capped off with a three-line envoi that contains all six teleutons.
the teleutons are tossed about again and again, reconstellated and recombined. often, different forms or different meanings (or even homonyms!) of the teleutons are used. and there are many ways a sestina can feel.
start writing! the sestina prompter will tell you what word to end the line with.
you can press enter (or click the enter button) to commit the line you're working on. don't worry about trying to make edits. the point here is not to write beautiful poetry; the point is to write anything at all.