Setting

1. Please install this add on:

https://addons.mozilla.org/en-US/firefox/addon/1865




2. and follow video:




                                                                                                                                      

(1)  select all: 

windows:    CTRL and A           

Mac:             (Command Key,Apple Key,cmd)   and   A

(2)  delete, copie and paste with right mouse function:
 

windows=  right mouse

Mac=        ctrl and click the mouse