<a href="website address here"target=new> what you want to say here </a>
Let's say you want to point to 123 stitch and have the link say 123stitch is a great website. It would look like this before you post then when you hit submit it will be a clickable link.
<a href="www.123stitch.com"target=new> 123 stitch is a great site </a>
If you want to practice the posting code to make sure it works then you can use www.practiceboard.com