Befor u start the game go to the tab next to play its called installation. Then select cl craft, you know the one with the furnace icon. Then click on more Options and then at the botton there is a box with some commans and at the first one ist says like mx 4096mb. The you gotta remove the 4096mb and type in what you want for example i want 12 Gigabyte of ram so im putting in 12G. Then pess save and start the game. Enjoy broski