In order to clear the cache and cookies, from your computer, you will need to, first, bring up your web browser, like Internet explorer or Mozilla Firefox. At the top tool bar, you will want to go to section that says "Tools" and click once. Then, scroll down to "Internet Options". Once this is open, you will see "Browsing History". You will need to click on "Delete". This will bring up a box with a list of options of information you can choose to delete. Although you can choose to delete anything you want, you will want to focus on deleting the "cookies" and "history". Cache and cookies can, also, be deleted by going to "My Computer". In here, you will find the option to go into cache and browsing history.
Chickens is right, you first need to know which internet browser you are using (Firefox, Chrome, Internet Explorer (IE) Rockmelt, etc) Then you can find the instructions on how to do so.
To find out which browser you have click 'Help' on your very top toolbar of your internet window, then select "About ___" (It may say "About Mozilla Firefox" or "About Internet Explorer" Once you click on that somewhere in the information window that pops up it will tell you the version of the browser you have.
Once you know which browser you have you can read the instructions here on how to clear the cache and cookies for your browser type: http://kb.iu.edu/data/ahic.html
f you are looking to clear your cache, clear your history etc. --> Tools -->Delete Browsing History --> Preserve Favorites (leave blank) --> Check Temporary Internet files --> Check Cookies --> Check History --> Click Delete