How does one remove temporary files from Safari? A friend logged on to her Facebook account using my iMac. Now I can't remove her e-mail address from Facebook. It was suggested to me that I try clearing temporary files from Safari but I can't find

How does one remove temporary files from Safari? A friend logged on to her Facebook account using my iMac running Mac OSX 10.7.5 and Safari 6.1.6. Now I can't remove her e-mail address from my computer. When I open Facebook her address shows in the user button. I do not have a Facebook account. It was suggested to me that I try clearing temporary files from Safari but I can't find anything that tells me how to do this. Are temporary files the same as the cache? It also was suggested that I try clearing Safari cache. How do I do that?