CMS Made Simple Forums

I am using an Apple Mac laptop.
Browser: Safari
However I believe that the problem is independent of the OS and the browser that I could (and do) use.
I am an experienced HTML and CSS author (and normally write raw websites)
I have been asked to assist with the website "avonvalleyrunners.org" because our web master is very busy.
I would like to add a menu (or rather a key to abbreviations) to the LHS below the menu already there on the page "http://www.avonvalleyrunners.org.uk/ind ... age=2012-2" but don't know how to do it or where to look.
I am new to CMS but can edit any page that I can find.
I can't find the menu pages and don't know where to look.
Is it possible to explain in 'simple' language what I should do?
Kind regards, Anthony

Sounds like you want to add a page.

Content -> Pages. Click Add new content. Add title, menu text and content (which you can update later).

Choose whereabouts in the structure you want the new page to be by selecting an option from the Parent drop down - this identifies the parent page of the page you are creating.

Submit, refresh the live site and edit the page as necessary.