How to change the options/preferences of a Mozilla Firefox/Thunderbird extension

Most of the extensions of Mozilla Firefox or Mozilla Thunderbird have "Options" dialogs. To open the "Options" dialog, you can:

Step 1: click the "Tools" button in the menu bar;

Step 2: select the "Add-ons" item;

Step 3: select the "Extensions" icon;

Step 4: select the extension you want and the "Options" button will show up;

Step 5: click the "Options" to open the dialog.