okay this one is easy
so after you make a poll there is the little box that has something like this

<iframe height="215" width="360" src="http://www.asianfanfics.com/poll/vote/73193">;<p>Your browser does not support iframes.</p></iframe>

right? copy it
go to the story you want to post it one
click edit chapter
then click source
scroll down to where you want to post the poll, it will look confusing a little with lots of <frame> and stuff but if you want it at the bottom scroll to the end
post the link you copied

click source again and save
simple ^_^ i hope i made sense o-o
let me know and if your lost we can go step by step :D