959Making a Bootable Installer for OSX
Straight from the Apple Support page:
How to create a bootable installer for macOS
https://support.apple.com/en-us/HT201372
High Sierra Page
https://support.apple.com/en-us/HT208969
High Sierra App Store Link (hidden from standard Search)
https://itunes.apple.com/us/app/macos-high-sierra/id1246284741?ls=1&mt=12