Fancy Nature is a resource pack. Nothing changes in your world until you enable it in the game's Resource Packs menu.
Enable the pack
1. From the title screen or the pause menu, open Options → Resource Packs.
2. Find Fancy Nature in the Available list on the left. If it isn't there, click Open Pack Folder and check that the pack file is inside your resourcepacks folder. Then reopen the menu.
3. Click the arrow on the pack to move it into the Selected list on the right.
4. If you use other packs that change leaves or plants, drag Fancy Nature above them. Packs higher in the list override lower ones.
5.
Check that it took effect
Go to a forest and look closely at the trees and plants:
- Leaves should look multi-layered and puffy, not like flat cubes. Oak and birch are the easiest to compare.
- Sweet berry bushes should show textured berries and fuller branch clusters.
- Dead bushes in deserts and badlands should look like fluffy 3D shrubs.
- Colors should still match vanilla. The pack keeps the vanilla textures and color palettes, so leaves won't suddenly change hue.
If trees still look flat, return to the Resource Packs menu. Confirm the pack is in Selected and that no other foliage pack sits above it.