Go to the link you wish to add. It will appear in your browser window (top of your screen beginning with http://
Highlight and Copy it (see separate blog on how to do that if you don't know).
Put your cursor where you want the link. Type a name for it. Let's say it's a link to whyquit.com Type WhyQuit then highlight WhyQuit, click on the blue icon that looks like a globe at the top of the comment box (it's in the same line with the B I U abc) and past the link in the URL to the right of the protocol box.
You can use this method for blogs and your profile page (by going into edit profile). In order to put in a link on someone's page, since there is no internet symbol, all you can do is paste it on the message board.