This process will help you block specified websites using Add-ons in Mozilla Firefox for Android: # Open Mozilla Firefox on your Android device # Tap the three dots in the upper right corner of the screen # Tap Add-ons # Search for Block Site # Tap on Block Site from the results # Tap on Add to Firefox button # Tap the three dots at the top right of the screen (if you can see it) # Tap Add-ons # Tap Block Site # Tap Options # Select options on the screen # Tap Save