Change readme example

webapp_admin/README.md

@@ -12,8 +12,8 @@ Reset WebApp settings
 Change free/busy to 36 months
 > python3 webapp_admin -u john --free-busy=36
 
-If you want to make a change for all users don't pass the user parameter. Example:
+If you want to make a change for all users pass the --all-users parameter. Example:
-> python3 webapp_admin --icons Breeze
+> python3 webapp_admin --all-users --icons Breeze
 
 # Dependencies