You enter the Repair console by booting the installer, clicking thru Language/keyboard screen, then clicking "Repair my Computer" link at the bottom left the next screen. Now ignore the OS found/not found to repair and click through to Recovery Tools list and choose Command Prompt.
Carefully type the exact commands in as they appear on the list.
Never click return on commands until you proofread each.
If this fails, you need to check the HASH on your download, then load ISO into ImgBurn, select Verify Disk, make sure it says Bootable in text at left, then verify both.