Q: where can i obtain a start up disk for my Macbook. I have not created it and need to reformat my HD/ Alternatively I need to get rid of the flashing question mark. My Macbook was purchased in 2009

I have tried starting my Macbook up with ALL the options given in your forum. Can someone please help me to with reformatting the drive? and where would i be able to download the OS? My Macbook is 5 years old. I would ppreciate it if the ''flashing" question mark can be resolved, Thx Kevin Bouah