Click on the icon, title, or url of the page that you want as if it was a link, or type the number corresponding to the page to go to it.
The Auto Dial page will automatically fill up the screen with links to your frequently visited pages. To open the page in a new tab, use the middle click button or hold Ctrl/Cmd while clicking (or pressing enter) just like any other website link.
You can remove pages from Auto Dial (and the location bar) by clicking the red X in the top left corner of each page.
There's various configuration values in about:config under firstname.lastname@example.org:
maxPerHost: Number of buttons to show for a given host
buttonSize: First row starts with buttons at most this wide
buttonRows: Grow the number of buttons every this many rows
typeTimeout: Milliseconds to wait before auto-selecting the typed button
Conflicts with other add-ons:
TabMixPlus: You'll need to configure TMP to point new tabs to chrome://autodial/content as TMP changes how new tabs are handled