Type a phrase:
highlight the phrase
Click the link button above the message.
That will put the code around the phrase.
After the first "url" type an equals sign
Type the http address.
Straight brackets are the correct kind, but I am putting a curly set here so it will show up as text:
{url=http://www.googledotcom}Go to Google{/url}
You only need to do this if the link is wider than the composition window for your reply.