Keyboard shortcut when adding extension to click “Add” and “OK”

[alphab3]

When trying to add a Firefox extension the browser asks the user if he would like to add this extension and leaves two options, one of the options is “Add”, I would like to know how I can press this prompt without using my mouse, also the same thing for the “OK” prompt when the extension has been successfully added.
In short - Adding extension without mouse.

[jscher2000 · Accepted solution]

On Windows, I get underlines on the access keys -- Add and Cancel -- that can be "clicked" with Alt+A and Alt+C, respectively.

Is that hidden on your Firefox? What about on right-click context menus, do you see those underlines for most items?

[alphab3]

You are a life saver! Thank you!!!!!