Note: Advanced steps mentioned below are intended for system administrators and experienced macOS users who know how to use the Terminal command line. Change the name of your drive to HighSierra. The system will automatically reformat the drive to make it compatible with a Mac. While an SSD would be a great option to create a bootable macOS High Sierra installer, a 16GB USB drive is enough as well. What’s next? Get an external drive you want to save the installer on. Alternatively, use this link to get the installation file.In this case, navigate to Purchased in the App Store and find the installer in the list If you’ve already upgraded to High Sierra, the installer is automatically removed from that location.Note, when the installer is fully downloaded it will automatically launch so make sure to quit it
The file named Install macOS High Sierra will appear in the Applications folder once the download is completed.
MacKeeper allows you to free up necessary gigabytes easily. Please note that before installing any system, you need to ensure there is sufficient space on your Mac.