You have to download Firefox Beta or Fennec to get custom addons though not sure for ios. For Firefox beta you probably have to do this first. Sign into the website mozilla addons because you may not see all addons. Then go into account settings and press create collections make a name. Be sure to write the down Collection name and the url User ID it provides. Add nos2x to the list extention. Then go to your Firefox browser settings click About page. On top of the page, click the Firefox icon 5 times. That enables debug mode. When you go back to the main settings. You should see Custom Collections button. Press and it will ask you to add User ID and Collection Name.