If there is a firmware password on your Mac, hold down the Option key until you're asked to enter that password. Step 2: As soon as the startup process begins, hold down the Option (alt) key and keep it depressed until you see the Startup Manager on your screen.

If you're using Boot Camp to start up from Microsoft Windows, set Startup Disk preferences to start up from macOS instead. Then shut down or restart and try again. Step 1: Insert the bootable USB into Mac and power it on.Some key combinations don't work when your Mac is using a firmware password.If you're using a keyboard made for a PC, such as a keyboard with a Windows logo, try a keyboard made for Mac. Or use your built-in keyboard or a wired keyboard. If you're using a wireless keyboard, plug it into your Mac, if possible.Some keyboards have a light that flashes briefly at startup, indicating that the keyboard is recognized and ready for use. Lastly, plug the USB drive into Mac and press Option key to select the drive from startup menu. Now, import DMG file and click Burn button to burn macOS dmg file to USB drive. Secondly, download UUByte DMG Editor and insert a USB drive.

You might need to wait a few seconds before pressing the keys, to give your Mac more time to recognize the keyboard as it starts up. Try your best to get it from reputable website like Apple, CNET, MacUpdate, etc.Then press and hold the key combination after pressing the power button to turn on your Mac. If you can't shut down, press and hold the power button for up to 10 seconds, until your Mac turns off. Click on the EFI Boot, so it will be used as the Startup disk. How to Make a Bootable Mac OS X Mountain Lion 10. Insert the USB Flash Drive, hold the option key and press the power button, this allows you to choose the Startup disk instead of booting right into the default disk. When a Startup Manager screen appears, click on the name of. If you can't get a key combination to work when restarting your Mac, shut down your Mac first. Step 5 Boot up MacBook with the USB flash drive. How to Use the macOS USB Installer Plug in the USB flash drive into your Mac.Press and hold all keys in the combination together, not one at a time.

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