There are 2 versions of the resource pack.
512×512 version requires at least 2 gigabytes of ram
1024×1024 version requires optifine and at least 4 gigabytes of ram.
How to install Laacis2’s Nature Paintings Resource Pack:
- Download the resource pack.
- Open Minecraft, and go to Options->Resource Packs->Open Resource Packs Folder.
- Drag the zip file you downloaded into that folder.
- Select the pack, and you’re done!