@Lindisfarne You do not need to root the device.
OEM unlocking is not necessary at this stage.
You need a Windows PC (running Windows) and you need to download one of the Android ROMs on the devices page for that device, unzip it and find the MSM Download tool.
Please read here to understand how to use the Tool and take your time.
Once the tool has finished flashing, the device will reboot, then you can set up Android, unlock the bootloader , set up Android again and then install UT.
I have not got the MSM Download tool to run on Linux or in a Virtual Windows machine within Linux.