Jen, when you go to start a new thread or reply to a post, look above the area where you'd type your message.

Do you see the white smiley face icon? The icon needed for creating a link is directly below the small, white smiley face. It's a blue globe with a small two-link chain.

If you type text you want to link to another site, run your mouse over the text to highlight it and, then, click the globe icon. That's when the small window will appear prompting you to insert the link you want included.

Another option is copy/paste a URL from your browser, when it's on the page you want to link to and then copy/paste that URL into your message.