The toolbar provided by Norton comes bundled with Norton Internet Security, Norton 360, Norton Security, Norton Security with Backup, or Norton Identity Safe. In order to restore it, update your Norton product to the latest version using Norton Update Center. The update will install automatically the toolbar and you will need only to activate it. For this purpose, I recommend that you follow the instructions provided by the support team: Mozilla Firefox, Chrome, Internet Explorer. Check the official web page for further details.
Note: If you don't want to update the Norton product, simply remove it from your computer and then install it again. After that, you will need only to enable the toolbar.