You need to play the game for a cumulative total of 10 hours. I don't believe this counts any time spent in the menus. You will come very close to if not surpass the 10 hours when attempting to complete both Story Mode chapters without dying. To earn this easier with no effort, set your PC or tablet to never sleep or hibernate and load up the first checkpoint in Practice Mode. Here your character will just keep repeatedly walking off the first ledge. You will need to confirm that you do not want to use a slow motion several times, but then he will just keep running without interruption. This method where you character is continuously walking will also help you work towards the "Moon Walk" achievement as well.