1. Make sure you are on Fabric version 0.13.3 or higher.

2. Make sure you have Origins version 1.4.1 or higher.

3. Go into your .minecraft > saves > WORLDNAME > datpacks folder (It should be somewhere in %appdata%, but here's a datpack installation tutorial: https://www.youtube.com/watch?v=Sfy7amIatf8)

4. Load into your world, if it's a pre-existing world, you may have to use an Orb of Origins to become Starborne.

5. Enjoy.