You should check out the FAQs, but besides that.....
You start a thread like you would any thread. Before hitting the submit thread button, scroll down the page and you'll see the option to add a poll with up to 10 selections. You check that box and then hit submit. You'll then get the options for the poll, like the question to ask and then the selections that you want.
There are several types of polls, too, but you'll see the options. It does seem that you get more answers if you make the answers anonymous.