Minecraft Forums

http://www.minecraftforum.net/topic/1723289-all-forge-rpg-the-legend-of-notch-reincarnation-beta-115-minecraft-rpg-mod-15-support/

It's important to read this:

1. Download this Mod (everything is included there)
2. Go to your .minecraft folder and navigate to saves
3. Open the .rar of this Mod
4. Go into: TLoN-WorldMap.rar
5. Drag the folder: TLoN-WorldMap into your saves folder
6. Go back to your .minecraft and navigate to bin -> minecraft.jar (open with WinRar)
7. Go into the .rar of this Mod again and openTLoN-Reincarnation Client.rar
8. Drag ALL the files into your minecraft.jar
9. Delete META-INF in your minecraft.jar
10. If you have a mods folder in your .minecraft rename/delete it!
11. Start Minecraft and select as world -> world!

with multimc you should just right click the instance you want to install the mod to, then edit mods.
have it on the minecraft.jar tab and click add, find the zip/rar file the mod is in and hit open.
multimc should do the rest.

if that doesn't work just do it manually