In the drop-down menu, select Manage add-ons.In the upper-right corner, click the gear  icon.To enable the extension now, click Turn it on.When the extension finishes downloading, click the Launch button.When you find an extension you want to install, click the Get button.You can also click the Search button and type a phrase or extension name.

A list of recommended extensions is displayed.Or, at the bottom of the menu, click Explore more extensions to open the Microsoft Store. Scroll down to browse suggested extensions.Click the More icon  in the upper-right corner of the window.Click Add extension in the prompt that appears.Once you find the add-on you want to install, click the Get button.In the upper-left section of the next window, search for an extension.In the new window, under Find new extensions, click the button.Select Manage extensions on the prompt that appears.In the drop-down menu, select Extensions.Click the Settings and more icon  in the upper-right corner of the browser window.When the installation is complete, a notification is displayed.In the upper-left corner of the screen, click the Add button.You can also browse recommended extensions using the category buttons. In the Find add-ons search field, type a phrase or extension you want to find.At the top of the page, click Extensions.In the confirmation box, click Add extension.When you find an extension you want to install, click the button.Search the store for a phrase or extension name, or scroll down to view recommended extensions.

Where to locate add ons in firefox