You need to read your manual. All manuals are available on the Dell site. The function keys are reached by pressing the Fn key along with a key on the HOME row, a to ; for 1 to 10. Therefore, F8 is . You can get F11 and F12 from and .   
How do I interrupt the boot up process on a Inspiron Mini 9 (910) to get into safe mode?
Boot into safe mode