First of all, you should ask your instructor or teacher to clarify the usage of actual Greek words in your poem. Once you've established that fact, choose your favorite character from a myth based upon what you think they did that was extraordinary. Then, pick a particular situation they were in that impressed you and start writing. As you write, relive the character's participation in the event and what they he/she did that amazed you. Use descriptive words, colorful imagery, and poetic devices. If you want, focus on one or two character traits that were admirable and that show their heroism. Maybe the story you've chosen has a moral that could be learned by others.
Don't choose the title of your poem until you've finished writing your rough draft. Reread it, proofread it, edit it, and then rewrite it in finished form. Make sure it is easy to read, flows smoothly, and conveys the message you're trying to give. Then and only then give your piece a title that will capture its essence.