Hey there! Welcome to the forums, and Hit & Run Online Multiplayer!
Regarding your question on how to play Multi-Meme Mod with friends, it should be as simple as downloading the mod from the thread, and then extracting the mod using WinRAR or 7Zip (either works). Once that's done, just drag the mod folder into the Launcher executable, and you should be good! A more in-depth guide on how to set up the Multiplayer Launcher is available here.
Hopefully that helps! If you have any further questions, please let me know.