Make sure Optifine is installed first! https://optifine.net/home

1. Open Minecraft
2. Click "Options"
3. Click "Resource Packs"
3. Click "Resource Pack Folder"
4. Move the .zip folder into the folder that just opened
5. Return to Minecraft and click "Done" (You need to refresh the menu to see it)
6. Click "Resource Packs"
7. Hover over Firewolf
8. Click the right arrow
9. Click "Done"