When the extension is first installed you will be able to see an icon in the status bar from which the extension can be used. When you "right click" this icon a drop-down menu is shown. From this the extension can be easily turned on and off (the extension is on by default), the options and about window can be opened and the results can be copied to the system clip board so the results can be easily stored.
If you open the options window. You can see a number of check boxes, in the default settings only the last one will be checked. The ILQ (Inbound Link Quality) check box. Which ones are used is a matter of preference. But some of importance is the Google PR, the Yahoo! inbound links, the Alexa rank, the links on the DMOZ directory and those from .GOV and .EDU site. But almost all the other values have some bearing on how your site preforms so it is a good idea to check them every now and again if you don't all the time.
Also in the option window there is a white list of sites you want the extension to work on. Below the box there is 4 buttons called "Add", "Edit", "Delete" and "Toggle". They all do exactly what you would expect, so I will not explain their function.
The last thing it might be worth noting is that all the results displayed in the status bar are linked to there sources, so you can confirm that they are accurate should you so desire.