Create macOS Sierra Bootable USB Drive Using Disk Creator

1. Download and install Disk Creator

2. Download macOS Sierra Installer

3. Insert an empty 8GB or bigger USB drive. 

4. Launchpad > Other > Disk Utility

5. Under External > click on Generic Flash Disk Media > Click Erase. Enter the following:

   Name: macOS 

   Format: Mac OS Extended (Journaled)

   Scheme: GUID Partition Map

   

6. Click Erase

7. Click Done

8. Open Disk Creator. 

   Select the volume to become the installer: macOS

   Select the OS X installer...: [Browse to Install macOS Sierra.app]

9. Click on Create Installer. Enter macBook user password > click OK.

10. Bootable disk creation in progress...

11. Click OK

12.Insert the Bootable USB disk and power up the macBook. Press option key. Select Install macOS Sierra image. Click on UP arrow underneath.

URL: http://lifehacker.com/how-to-make-a-bootable-macos-sierra-usb-flash-drive-1786853248