Click the Add button and your extension will be installed.
Click on + Add to Firefox button and the Software Installation window will appear after the add-on has been downloaded.
Click and open the add-ons details page.
I would recommend you take a look at the ratings of each add-on before you download it.
Select the video downloader of your choice.
This will open the search results in a new tab.
Now within the Add ons Manager search bar, look up for video downloader in the Find more add-ons field.
You can also open using the Firefox keyboard shortcut: Ctrl + Shift + a in Windows or Linux and ⌘ + Shift + a on Mac. This will open the Firefox Add-ons Manager window.
Choose the Add-ons option from the list.
Click on for menu options located on the right-hand side.
Launch the Mozilla Firefox browser on your computer.