1- Press Windows + R key ( or windows search since both work )
2- Type in %appdata% then go to .minecraft and then saves.
3- Choose the world you wanna use the pack on.
4- In that world's folder you must see a folder called "datapacks" if not, then create one. (If the world was created in an older version you might not see it. But the pack works on the newest versions only)
5- Put the pack in the datapacks folder and open the game.
6- You might need to use /datapack enable "file/DrugsDatapack" command in order to enable it. Or to test it just do /function drugs:load
7- Use the command to get the drug /give @p carrot_on_a_stick{display:{Name:'{"text":"Drug"}'},CustomModelData:69} 1