Mac OS Repair Service 2 in 1 Bootable USB Flash Drive installer with El Capitan and High SierraFash drive USB 3.0 fast and efficient, you can reinstall fresh, wipe system, restore, upgradeWorks on Intel Macs with the OS flash drive
2.restart computer upon restart before the chime hold down the option key (you might have to try a couple of times)
this will take you to the booting screen
3.usingthe cursor keys choose the operating system then hit enter
4.oncein the installer you can install from there by following on screen instructions