(1) Remove the extension by right-clicking on the extension icon on the Chrome toolbar, selecting "Remove from Chrome", and then clicking on the "Remove" button.
(2) Open www.bookmarkninja.com in your browser and select "Tools/Install Browser Buttons" from the main menu of Bookmark Ninja.
(3) Under "Install Browser Extensions", click on the links next to the Chrome icon ("Install the 'Add to Ninja' extension for Chrome" and/or "Install the 'Bookmark All Tabs' extension for Chrome") and follow the steps provided.