Mac Book 10.58 runs too slowly! Help, please!

My daughter has an older MacBook from 2008 or 2009 with OS version 10.58. It's running VERY slowly.

I have a PC and when mine runs slowly, I can easily delete temp files, delete history, delete cookies, etc. using buttons on my PC. She has not found a way to delete similar stuff on her Mac, and I don't know how to advise her. Can anyone supply a few steps she can take to get rid of all that stuff that may be slowing her down?

Also, I've suggested AVG and a few other free antivirus/antimalware programs, but she has checked and says they can't be downloaded because her OS is too old. Does anyone know of a similar free program that would work on her Mac Book? She's not working right now so can't afford to buy a new one. Many thanks! BTW, she is even more a "newbie" than I am...