(Had someone ask this question via the contact form.)
To add a poll to a new thread that you are creating, enter the post, but do not submit it yet.
Look near the bottom of the post composition page in the "Additional Options" section and you will see a "Post a Poll" sub-section.
(If you do not see sub-sections below the "Additional Options" header, you need to expand that section first, by clicking the down arrow on the right of that header...
)
Enter the desired poll options & submit your thread. You will be prompted to enter poll questions & answers on the next page.