first thing you need to do is Install forge to your vanilla launcher.
Download the installer or win installer from the forge website and when you run it use "Install client". This will get forge into your vanilla minecraft versions list.
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Next open up your minecraft folder and make a new sub folder with the name of your pack no spacing, no capitals.
Inside that folder that you just made you will need a few things, ".oricle_jre_usage", "minecraft", and "natives" folders as well as a version file.
The oricle, natives and version can be pulled out of any modpack you have already downloaded with FTB of the same minecraft version. The minecraft folder can just be made
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inside the minecraft folder (the one inside your pack folder) create 2 more folders named "mods" and "config"
Put any mods from your pack in the mods folder and any config files from the pack in the configs folder.
Your pack is done, now you need a profile for it on the launcher.
Run your minecraft to bring up the launcher but don't press play yet.
Down in the bottom left click "New Profile".
The profile name can be anything, I normally name it the pack name.
for game directory it should already be aimed at your regular minecraft folder you just add "\mymodpack\minecraft" to the end of it. Of course using the name of the folder you made instead.
for "Use version" select the forge version you installed
and it's VERY important to turn on "JVM Arguments" and put in
Code:
-Xmx3G -XX:PermSize=256m -XX:MaxPermSize=512m -XX:+UseConcMarkSweepGC -XX:+CMSIncrementalMode -XX:-UseAdaptiveSizePolicy -Xmn128M
this is what I found to be the best arguments for running a mod pack. In fact I find pasks run MUCH smoother using these arguments on vanilla launcher than they do on FTB. lol
your profile should look like this:
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Save profile, and select it.
Your Mod pack should be ready to run, press play.
This process is repeatable so you can have MANY mod packs on your vanilla launcher.