It should be dead easy to use the Forum.
To begin with you'll see a list of topics, with the busiest ones at the top. To see what people are saying about a particular topic, click on its name. Any topics which haven't seen any action for over three weeks are listed separately by clicking 'old topics'. If none of the topics covers what you're interested in saying, you can start a new topic.
When you're looking at a list of comments, you can do one of three things. You can either reply to a particular message by clicking on 'reply to this', or you can make a new general point by clicking 'post new message'. Thirdly, you can start a new topic of discussion.
Polls are a way to vote for stuff. Anyone can create one, add things to vote for, and vote for any of the options. If your browser has got the Flash 6 (or newer) plugin, the current state of play is shown in the groovy pie chart!
If someone's already started a new poll. you'll be able to vote for the things already there, or there's an area lower down on the page where you can add stuff of your own to vote for. You can still post messages as normal, which appear at the bottom of the page.
To create a new poll, just fill in up to six options for people to vote for. The names of the options should be quite short, because there's not much space for them in the pie chart. If you want to offer more than six options, just add extra ones you need one at a time on the voting form.