1. Locate your datapack folder
If your world is already existing this folder can be found by selecting the world in the menu, then pressing "Edit", followed by "Open world folder", then open the "datapacks" folder.
If you want to create a new world go to the "More" tab, then press "Data Packs" and then "Open Pack Folder".
2. Move the datapack
Copy the Magic.zip file you downloaded into the datapack folder.