I'm trying to remove the app that I used to install it and trash won't let me. I am not planning to upgrade to High Sierra any time soon. I'm guessing that at some point I must have downloaded the update but never installed it. I just checked my applications folder and there is an Install macOS High Sierra file this is 5.21 GB.Click the Apple icon in the top left corner of your screen and choose Restart from the menu. Back up your Mac before you begin (just make sure you didn’t forget to do it). Here’s how you can reinstall the macOS High Sierra and keep all files and user settings.Its size automatically adjusts to fit your content. And because storage space is shared across APFS volumes, you don't need to reserve space for the new volume. If you install macOS on an additional volume of your startup disk, you can switch between that macOS and the macOS on your other volume, as if each were on a separate disk. Can I Delete The Install Macos High Sierra Apple.