Not hard info to find but i figured having a brief example readily available on the forum wouldn't hurt. 1. Go to the optifine site and choose the latest HD Ultra download. You may not need all the features the ultra pack gives but it won't hurt most of the time. 2. Open ftb and click on the Edit Mod Pack button. 3. Click on the second tab JarMods and then click on Add Mod. 4. Find where you downloaded Optifine and select it. Once you do this Optifine should show up in the Enabled Mods field. You then just launch FTB as normal. If you have never used Optifine before you will notice a rather large change to the options menu and will also probably notice a huge change in playability of FTB. Currently the only conflict Optifine creates is that the large nameplates and speech bubbles from voxelplayer do not work, but it is a very small trade for the performance boost you receive.