Before you start to post the poll, you may want to put a little thought into the question and the poll options; maybe even write them down to see how they will look/sound. I think there is a max of ten response options, so don't write up a poll with any more than that. When you're ready...
Click the "New Topic" button to start a new thread.
Enter a title for the thread/poll, and in the text box, add a brief explanation of the poll, and any details you think might be helpful. Be aware -- not all folks will read the description before voting.
Down below the text/message entry box, there is a box with other options that looks like this:
The red arrow marks the block you need to check to add a poll. Click that checkbox, think about the number of response options you need and change the number in the nearby box to reflect it, and then hit the Submit New Thread button that is BELOW the checkbox (near the bottom of the page).
It will start to process the new thread just like a normal one, but then you'll get another page with poll options; it looks like this:
Fill in all the info, then I recommend you use the Preview Poll button to see what it will look like BEFORE it is published/posted to the site. If necessary, back up and make any needed changes, the re-preview to make sure it's what you want.
Click the Submit New Poll button when you are done and ready to have it posted to the site.