You will need Xex Menu to do this.

Tutorial Below
It will not work from an External HDD.

Official Microsoft Hard Drives formatted through the NXE should already contain the correct HddX partition for Xbox1 support, it just lacks the needed compatibility files. If you have an official Microsoft HDD and you can see a HddX partition on the drive in the file manager, skip steps 5-9.

Steps
1: Download the files used for this tutorial
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2: Extract the downloaded files to a flash drive or external usb hard drive formatted to FAT32

3: Lanch Xex Menu

4: Press RB until you see Hdd1, then press right on the Dpad until you find one that says "Usb1". (Top right hand corner)

5: Press A (open)on the HDDXFixer folder. (Just a quick update, HDDXFixer will leave all of your current filesystem intact and make no changes to your files/games etc.)

6: Hover over the default.xex and press A to launch HDDXFixer.

7: In a few seconds you will be presented with some text. Just follow the instructions saying yes to any confirmation messages. It will tell you when it has finished.

8: You need to restart your Xbox for the partition changes to finalize.

9: Once you have restarted your Xbox, return to Xex Menu and navigate back to Usb1: (Shown in step 4)

10: Press A (open) on the Hacked Xbox1 Emulator folder. You should see a folder labeled Compatibility.

11: Hover over the "Compatibility" folder and Press "Y", you then Navogate down using the Dpad and press "A" on copy.

12: Now press the right side of the Dpad until you find HddX in the top right hand corner.

13: Press "Y" over the compatibility folder and Press A on delete.

14: When that is deleted press "Y" and then press "A" on paste.

Thats It! Now you should be able to play nearly all Xbox1 games.

Credit to : [ Register or Signin to view external links. ] for helping me find all the info and gather it into one thread.