Project: Parasite Infection is intended for multiplayer it is possible to play singleplayer but your experience will be much harder alone.
Here is a tutorial on how to use the Essential Mod witch is what this Modpack uses for multiplayer.
Project: Parasite Infection has many of the mods that RLCraft has so if you have played that a lot of this will be easy. I also recommend Downloading and installing Optifine into your game I also use Sildur's Vibrant Shaders if you download them I recommend Downloading High if your system can handle it If you can not I recommend going lower. 
You can find the mods being used in the Relations Page near the title of the Modpack. I encourage people to make videos about the Modpack as long as they credit the pack in the description of the video. This Modpack is inspired by Troubled Boys Scape And Run series and NeoCranium's Parasite server.
- Edition: Minecraft Java
- File type: .jar
- How to install: Install the matching mod loader (Forge, Fabric or NeoForge) for your Minecraft version. → Download the .jar. → Put it in the .minecraft/mods folder and launch that loader profile.
- Where to get it: Opens on CurseForge — not every file is mirrored on our own servers.
Install steps are the general flow for this file type — How to install Minecraft Java mods & modpacks walks through it step by step.
Project: Parasite Infection is a free Minecraft Java modpack. Downloaded 3,500 times (via CurseForge). Download it and open it directly in the game.