This pack is simply Minecraft 1.6.4 with FML and NEI to add your own mods to.
To add mods on Windows XP:
Click Start > Run and type (without quotes) "%appdata%\.technic\modpacks\build-your-own-modpack\mods" and copy mods there
Windows Vista/7
Click Start and in the search box type (without quotes) "%appdata%\.technic\modpacks\build-your-own-modpack\mods" and press "Enter"
Mac:
In Finder on the top bar click "Go" then click "Go to folder" and type ~\Library\technic\modpacks\build-your-own-modpack\mods and click go.
To add mods on Windows XP:
Click Start > Run and type (without quotes) "%appdata%\.technic\modpacks\build-your-own-modpack\mods" and copy mods there
Windows Vista/7
Click Start and in the search box type (without quotes) "%appdata%\.technic\modpacks\build-your-own-modpack\mods" and press "Enter"
Mac:
In Finder on the top bar click "Go" then click "Go to folder" and type ~\Library\technic\modpacks\build-your-own-modpack\mods and click go.