Hi Lin
I'll do my best to explain but I can't promise!!
You type in the words you want to use to create the link, for example FACTSHEET. You then need to have the URL address you want to link that to - eg
http://www.alzheimers.org.uk/site/scripts/documents.php?categoryID=200137
I always open the page I want in a new window and highlight and copy the address ready to paste when I need it.
You highlight the word FACTSHEET then clink on the little icon above the reply box which looks like a little globe, the one next to the globe with the red cross on it. This gives you a little box which asks you to put in the URL address you want to link to. I always take out the http thing which is already in the box and I then paste in the address which I have already saved. That's all you have to do as the word will have turned blue and it is a now a hyperlink -
FACTSHEET
I bet that's as clear as mud!!!! The instructions may be in the Help area but I can't see them at the minute.