First things first, let's make sure you're logged in to your account. If you're not already logged in, do so in the frame below.
Once you've logged in (or if you are already logged in), you'll now be looking at your profile page.
This is a bit like your Facebook wall. It's where all your status messgages are kept, and where your friends come to post on your wall. To write your status, simply click in the box that says "share". When you do this, the box will expand. You can see some formatting options at the top such as Bold, Italics and Underline, as well as ways to add links and pictures. At the bottom you'll find some more links. You can use these to upload pictures and files from your computer, share websites with a bit of preview text, or embed video and audio files from elsewhere on the web. You can also set your post location here.
Once you've finished writing your post, click on the padlock icon to select who can see it. If you do not use the padlock icon, your post will be public. This means it will appear to anybody who views your profile, and in the community tab if your site has it enabled, as well as in the network tab of any of your contacts.
Play around with this a bit, then when you're ready to move on, we'll take a look at the Network Tab