How can I clear my cookies and caches on iMac?

I have a site that sends requested images. By clicking on an image it provides me with further images of a similar nature (I can assure you that these images are old movie stars, and nothing more). Recently I lost the facility to click on an image. Iasked the site for advice and they said that I should clear my cookies and caches, but I am afraid that my tech savviness doesn't stretch to that. Can someone advise me as to where I would find these on my iMac

[Re-Titled by Moderator]