With optifine's new installer that only works with regular minecraft. Installing optifine can be really quite confusing. But when your done reading this article, you'll be bashing your head against the wall asking yourself "Its so simple, why didn't I think of that!?" Now, for those who are just looking for the mod file. Your answer is quite simple. That jar file you downloaded from the optifine website is both a installer AND a mod file. So go ahead and chuck that into your mods folder and have fun. For those who want a more in depth guide. Here's your step by step. (I'm assuming you've all-ready downloaded ftb.) 1 - Download optifine. https://optifine.net/downloads Look for your minecraft version. And chose the variant you prefer. The top of each variant list is the newest version. 2 - Locate your ftb folder. When you first run ftb, it will ask you where you want it to place its folder for containing the mod packs. If you don't remember where it is, run the launcher, go under settings, and it should say at the top.(You can even change it if you want to.) 3 - Locate the mods folder for your mod. Its normally somewhere like the following. FeedTheBeast/(Your modpack here)/minecraft/mods 4 - Drag and drop (or copy and paste) the optifine jar file you've just downloaded into this mods file. (If you've tried to run the .jar, you may have noticed its a installer, don't worry, it works as the mod itself aswell.) 5 - Run the ftb launcher, select your modpack, and hit edit modpack. You should be able to see optifine has been automatically added to the Enabled mod's list. If not, click "add mod" under the disabled mod's list, and find the jar file you just placed in the mods folder. 6 - When you run the modpack, you should see optifine there in all its glory.