Work in progress
Most websites will have a certain number of special pages. For example, the default front page does not offer an "Edit" link since the page is automatically generated from the latest 10 posts. That page cannot be assigned meta tags by editing the page, instead you need to go to the administrative screens of the Meta Tags extension.
Click on the Admin tab of your Toolbar, then click on Settings.
In the list of settings, look for Meta tags under Content management. (Admin » Settings » Content Management » Meta tags) Click on it to enter the Meta tags administration screen.
At the top you see a set of tabs, click on Custom Pages Meta Tags.
That page lists all the pages that you already customized. Click the edit link to modify the Meta tags on those pages.
To add new pages, use Add tab at the top. This brings you to the Meta tags editor. The following are the different entries you want to fill:
Future versions may include an easy link on all pages so one can edit the Meta tags without having to go to the administration screen.