Once you have installed Seerobots the plugin will appear in the status bar on the bottom of your Firefox browser and may look something like:
In the first Version of Seerobots only the Meta-Robots are shown instantly. X-Robots are shown on demand. As you can see in this example there is one area that says "[Click]". If you do a mouseclick on that area ...
... Seerobots will show you the X-Robots settings for this page.
Enjoy and kindly rate the Addon over at Mozilla