I'm not sure what you want to do. You can see the add-ons in Add-ons and Themes in the menu (shortcut ctl+shft+a) and set permissions, access preferences and otherwise manage them. Depending on which add-ons you have installed, they may also have added buttons to a toolbar in the browser. You won't see a button in private browsing mode unless you have allowed the add-on to be used in private windows; that is one setting you can change in Add-ons and Themes.