Link button not working in text and images toolbar

[JulieR]

Hello
I am trying to create links on my web pages such as link the text "contact me" to the contact form on the contact us page but I can not get the "link" button to work.
I am sure I am doing everything right (but I am very new to this!) - I am highlighting the text, going to the "link" button, and on pressing it the toolbar disappears! I believe (from watching tutorials) that an options box should pop-up showing where I want to link it to.............
Some of the other buttons on there don't work either e.g. the text colour, but the font size button works ok.
Please can someone tell me where I am going wrong or how to fix it?
Many thanks
Julie