To post to the forum, you'll need to make an account. No big deal, just keeps the riff-raff out, mostly.
Start a new post by clicking the "Start a Discussion" button found just about everywhere, or click "Write a Reply" at the end of a topic to add to it.
You can use basic Markup syntax to enhance your post:
You can make text
**bold** by using asterisks, see? This is italic and this is bold.
You can add headings to your text by using a # before your heading text. One # will make the largest heading, six #'s will make the smallest. Here's an example:
This is a Heading
That was made like this:
### This is a heading
To add a link to your post, simply put square brackets around the text you want to be "clickable," and put the address of your link immediately afterwords, in parentheses. Look:
This line will have a [link](http://example.com) in it!
This line will have a link in it!
There's more available, but that'll certainly get you started. You can always try things out, and see what works. Posts can always be edited after the fact; just click the "..." that appears when you hover over the bottom corner of a post you wrote, and choose "Edit."