1) Download Optifine from the OFFICIAL website (other sites might be harmful, make sure the website you're on is http://optifine.net) ► optifine.net/adloadx?f=preview_OptiFine_1.9.0_HD_U_A1_pre.jar 2) Open the file you just downloaded, and a installer will pop up. You just have to click "Install" 3) After a couple of seconds, another window should pop up, saying "OptiFine is successfully installed". Click "OK" 4) Open up your Minecraft Launcher, and Optifine's profile should be automatically selected. If it's not, click on "Edit Profile", and in the versions field, select "release Minecraft 1.9-OptiFine_HD_U_A1_pre" 5) Hit "Play" and join Cube! ► Keep in mind this is a preview version, so there might be some bugs, but all bugs are hopefully gonna be fixed in future versions!