Nice guide if your recovery OS is an older version and/or doesn’t work, you can install from a USB drive:
http://osxdaily.com/2014/10/16/make-os-x-yosemite-boot-install-drive/
Nice guide if your recovery OS is an older version and/or doesn’t work, you can install from a USB drive:
http://osxdaily.com/2014/10/16/make-os-x-yosemite-boot-install-drive/