To post a poll you have to start the thread, so type out your thread title and text, now croll down till you see this bit.
A; Check the box to include a poll with your thread.
B; Choose how many options you want in your poll, maximum is probably 10.
C; Click on Submit New Thread.
You will now be taken to your poll, got to do this quick because your thread is now posted and you will get dumb comments like "there aint no poll".
Type in your poll question, you can change the amount of poll options if you wish, I normally just make it 10 and use however many I want each time, ie you don't have to fill out the 10.
Fill out your poll options and check the boxes you want on whether it is a private poll, multi choice poll etc etc, now click submit.