hit tools and go to the internet settings and hit edit and hit select all and all

cookies will be blue and hit file and delete. all cookies gone.

are some are different you go to internet delete and your need to go to

delete and a menu will ask what you want history and stuff remove all checks

and put a check to cookies and delete the cookies

Go to Gibiru and get cookie crumbler.

It would help if you told us which browser you were using.