Couldn't figure out to enable addons manually in Firefox beta 66 for some reasons? Sorry for my fool question (I admit I must missed something really  obvious). But what's the official way to enable a desired addon in  private-mode in my FF version 66.0b4 (64-bit) Beta. In normal Firefox, I  go to Addons in menu or

    about:addons

both of them doesn't provide any checkbox or visible options to turn on a given addon (I clicked into addon, too, didn't work so far, only there's automatic update options). In private-mode Firefox, I type

    about:addons

just went to a blank page. So what's the steps? (There's no UI part of that task on addons page so far, I search in web  and see what it looks like but seems like in my FF there's nothing like  that, only autoupdate options)