There's info in the FAQ on how to create polls, but since this is new software to many of us (It took me a minute to figure out how to create one) I thought I'd post the quick info here. You can also find info on other functions of the board by typing in keywords to the FAQ search.
To create a poll when you post a new thread, simply click the 'Yes! post a poll' checkbox at the bottom of the page, and set the number of possible responses you want to include.
When you click the submit button, you will be taken to the poll creation page, where you can specify the question and the list of responses you want to include.
You may also want to specify a time limit for the poll, so that (for example) it only stays open for voting for a week.