If you already have Minecraft Forge or FML installed, you have two options for installing LiteLoader:
Install LiteLoader and extend from the Forge/FML version.
Install LiteLoader as a mod (see below).
LiteLoader supports being loaded as a mod by other Mod Systems which recognise the TweakClass metadata entry in the jar file. Currently only LiteLoader and FML support this entry, but other Mod Systems may do so in the future.
To load LiteLoader with another ModSystem, take the following steps:
.minecraft/mods/1.7.10
for Minecraft 1.7.10)LiteLoader will now be loaded by the other ModSystem when the game starts up.