Enabling or unlocking OEM tends to help you manually open the bootloader by using a tethered fast boot mode. So to do so, you should begin by heading to the settings menu. Once you click on About Phone and tap Build Number 7 times, a specific menu called Developer Options will appear. This particular feature is enabled for android operating systems either using android 5.0 or later. In the Developer Options menu, you will also find an option called OEM Unlocking. So the next step is to enable the same as it allows you to unlock particular aspects manually. To know about OEM click here.