Delete Cookie in Firefox

When I test paypal code in paypal sandbox:
 https://www.sandbox.paypal.com
Due to that I typed wrong password, I can not access Paypal Sandbox anymore due to cookie set.
To remove cookie stored in Firefox,
1) Go to Firefox->Options
2) Select the Privacy panel.
3) Set Firefox will: to Use custom settings for history, select show cookies.
or click the link: remove individual cookies
4) Type sandbox in search box
5)  Select the cookie(s) in the list to remove and click Remove Cookie.




To remove all cookies:


1) Go to Firefox->Options
2) Select the Privacy panel.
3) Click the link: Clear Recent History....
4)  Set Time range to clear to Everything.
5) Click check-box of Cookies  and Click Clear Now