There's an even easier way (for varying values of 'easy'):
Write what you want to say.
Then 'select' the words you want to turn into a link (ie, right click and hold while you drag the cursor over them).
With the words selected, click on the URL button. This will give you a result [url]like this[/url].
Now, put you cursor after the letters 'url' in the first brackets and add an = sign [url=]like this[/url].
Finaly add the URL of the link just after the = sign [url=
http://www.example.com]like this[/url].
I've disabled the code in this message, so that you see what happens without it turning into a link. It looks a mess as text, but when you get used to it, you can just type it out in full as you go, without needing the URL button at all. You can also paste a URL from your clipboard with Control-V, so you can do it all from the keyboard, if that's easier for you.