First of all, we're trying to help you out in getting your question answered. So please be a bit more courteous when responding.
Second of all, it is mooore likely that after the creation of your thread, the ability to make a poll becomes unavailable. So, the only way to do so is to follow what Zekrom mentioned: just contact any of the mods of the section where said thread is located, and they'll be more than happy to add in a poll for you. I was also going to say "you can also make a new thread WITH the poll", but I think the former is more easier and quicker.