These are special mods that expand Minecraft beyond the 32bit integer limit. For any support, contact the Cursed Creations team at https://discord.gg/gBXj5j55uf
To install this first start off with downloading inf-20100630 from here. Manifold is necessary for these mods. Install Manifold as a JAR mod via the "Add to Minecraft.jar" option in MultiMC-based launchers.
Note: These versions are very CPU and RAM-intensive compared to their vanilla counterparts. Do NOT expect to have the same performance as typical 64-bit mods, even at spawn.