The official google page is here.
Once installed, you'll see a new icon appear in the toolbar next to the location bar. If you haven't set your bloglines user name, you'll see the following:
If you click this option you'll be sent to the preferences page, where you can set the user name:
If you've set a valid user name, you'll see the number of unread articles for that user name:
Clicking this icon brings you to your bloglines account: