There are several things you need to consider (I've got a feeling this is going to be a long answer so please bear with me).
One of the first is whether to go for a free site or one you pay for. Personally I wouldn't consider a free site as there are too many drawbacks. In many cases what you're wanting to do won't be possible with a free site.
It sounds like you're wanting to create a forum and to do this you'd need to be looking at using scipting tools like PSP and SQL - don't worry of these don't mean anything to you, the important thing is that most free sites don't support PSP or SQL.
I answers a question regarding free websites which explains more of the pros and cons of free sites... https://answersrip.com/question/index?qid=20060812224233AAMT2j7
On the basis you're going for a paid website the next thing to do is to get your own domain name (you can't do this with free sites) and some webspace (where your site will be hosted). You can do these together and my recommendation would be to go with IX Webhsoting - they've been voted webhost of the year 2003, 4, 5 and 6 and their packages start from just $3.95 per month. For your $3.95 you get a massive 20Gb of diskspace and 2 domain names. For $12.95 a month you get unlimited space and 10 domain names.
The advantage of having several domain names is that you can register all the similar names and have them all link to one site. So instead of having just mywebsite.com you can have mywebsite.net, mywebsite.org, my-website.com and so on. Important, especially if your site becomes popular, you don't want to lose visitors because they entered an incorrect address and worse, you don't want some dubious website cashing in on your success by starting a site with a very similar name.
IX Webhosting site - http://www.ixwebhosting.com/index.php/v1/pages.dspmain
IX Webhosting review - http://www.thehostingchart.com/ixwebhosting_review.html
The top 10 webhosts reviewed - http://www.thehostingchart.com/
Once you've found a webhost you like you can register a domain name through them. Unless you have a specific and unique name in mind you're likely to find that a lot of the names you want have already been registered, you just need to keep trying new names until you find one that's available. Also check out the availability of the same name with .com .net .org .info etc - you don't want a website that has a very similar name to a porn site for example.
You'll need a credit / debit card to hand when registering and once done you'll have to wait a little while for your domain to become active (usually a few hours but can take a day or two). Once active you can start with designing your website.
Website languages such as HTML (Hyper Text Markup Language) may seem completely alien but you'll soon get the hang of it. HTML is the commonest website language and is good for most things. There are a few basic commands such as inserting images, changing the size and style of the text, creating a basic table etc and once you know these you can put together a reasnable site. The good news is that you don't really need to know the language as programs like Frontpage will do most things for you.
If you're familair with MS Word then the transition to Frontpage is easy as many of the menu commands are the same - just point and click.
Having a forum is the key to your site as this will allow users to post comments and replies. You can tweak the settings so anyone can join in or set is so that registration is required.
For a forum you'll need something like PHP but the good news is that mot of the decent webhosts will provide you with a ready made forum for free so all you need do is transfer it to your webspace and customize it with your own colors, logo etc.
If your webhost doesn't provide a ready made forum then you can get one for free and the most popular is phpBB (but your webhost must support PHP).
As for creating the rest of the site, this is a huge area and there are lots and lots of excellent websites with step by step instructions and pretty much everything you could want to know. Here's a few to get you started...
http://www.w3schools.com/
http://www.pagetutor.com/
http://www.entheosweb.com/website_design/default.asp
http://websitetips.com/
http://www.htmlgoodies.com/
Good luck with your site.