1) How do you add/edit/remove links from the page navigation?

<a href="default.aspx">Home</a>

Default is the page name & Home is the page title. when you want to link to another page or website you use <a href>

2) The page is centred by default - how do you left or right align the page? 

In Internet Explorer, by default the page is centered. But in Firefox and Chrome the page is left aligned by default.

you can change the alignment by doing the following

<table><tr><td align="left">Your content here</td></tr></table>

3) How to change background Images?

<table style="background-image: url('images/yourimage.png');">

This will help you add background images

You will have to learn html to start doing these things. A very simple and easy to understand tutorial is available for free at

http://www.w3schools.com/

They are authoritative & the tutorial is very easy to learn. 

Hope this helps.