As you win referendums you will unlock additional social policies and powers. You can check your progress by hitting left trigger, going to colony control and using the left and right bumpers to locate the screen. Once you have 10 available select them. You should see the little box show green if selected. Once you do that it will unlock. You can actually pause the game, highlight everything, unlock the achievement and then deselect what you don't want before resuming the game.