- Open firefox borwser
- In the menu, go to tools, and click options
- In the options window click privacy tab
- Under private data section, click settings
- Now select,the actions you want to clear by putting check to each box
- Now in private data section select "always clear my private data when i close firefox"
- Now click ok
if you don't want prompt each time when you close firefox and you want to run cleanup process automatically just deselect " ask me before clearing private data" in a private data section and click ok.