I'll try to give you step by step instructions.
1. Click Reply to a posting, or start a new topic. Type in what you want to say. It will look something like this:

2. Highlight the words you want to make into a link. To highlight the words, go over them with your left mouse button held down. Then you are going to click on the little Link button that I've indicated with a red arrow below:

3. When you click on that Link button, you'll get a popup asking you to enter a url. Enter it as I have done below for mobclan. Then click okay:

4. When you save your message, it will end up like this:
The website to mobclan is
click hereIf you don't get the editor when you click "Reply" or "Add a Topic," then you need to go into your personal profile setup and select for it to give you the editor when you are making posts. Also, you will not get the full editor if you hit "Fast Reply" 'cause it's not available in that mode.
Hope this helps.