uslolds

ok i am new to using all this computer stuff! how do i take a screenshot?

i have ccleaner but dont know how to use it! its picking up registry files that needs to be fixed dont know what to do cuz i was told one wrong move then our computer is wiped out! second under startup under tools i dont know what can be uncheck and everything still works! i am taking up more processors then it did when it was brand new, i dont understand & dont know what to do? when i 1st got it it was taking up about 40% now its 52% +? please help thank u so much uslolds