Like this?
Right, first thing is to copy the URL you wish to post.
Then type your reply, and highlight the word that you want to be your link.
Then click on the wee symbol underneath the smiley face on the panel above the reply box - it looks like the Earth with a paper clip at the bottom.
When the pop-up box opens, paste your link in there. It has to be a proper link with 'http://' at the start.
Edit: If you don't get the panel above your reply box, you will need to go into your Control Panel and turn on WYSIWYG editing under Settings & Options > Edit Options > Miscellaneous Options.
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