You can create this using either built-in tools or third-party applications.
: Use apps like DiskMaker X , which automate the process through a simple interface.
: Obtain the full macOS High Sierra installer from the Mac App Store or use a tool like Mist to download it directly from Apple's servers.
: If you only have access to a PC, you can use TransMac to restore a High Sierra DMG file to a USB drive. Key System Requirements & Features