Henndro Joshua :
How would i go about to make it use the gtx850? I have already set it to use the high performance nvidia processor. Does this have anything to do with Nvidia's optimus thing?
Nvidia's Optimus can cause problems with certain games. In a laptop using Optimus, the Intel integrated graphics
always drives the screen. The nvidia GPU is used as a coprocessor, which sends the completed screen image to the Intel graphics for display.
If the game is not coded to properly recognize the presence of a GPU "coprocessor", it may end up only detecting and using the Intel integrated graphics. I've seen this happen with a lot of older games - they were coded in an age when there was only ever one GPU in the computer. So after they detect one GPU (the Intel), they stop looking for any more GPUs.
League of Legends is a pretty major title though, and I have to think they've updated the game to work on Optimus laptops. Make sure your nvidia drivers are updated, and that you're running the latest LoL version.
If you can't get it to work, look in your BIOS settings. Some laptops allow you to disable the Intel integrated graphics, leaving the laptop to run on the nvidia card only (at a cost to battery life). Another non-optimal solution is to use an external monitor. The HDMI port on most dual-GPU laptops is connected directly to the nvidia card. If you connect an external monitor and display only to it, the game will detect the nvidia GPU as the "main" graphics card.