To check your variant type go into your phone settings, navigate to "About Device" and then your variant will appear under "Model number" in my case my model is the G900H. Take note of your build number too. Once you have these things, go check on
http://www.sammobile.com/firmwares/ for your variant and the latest software updates will be displayed there, you can use Samsung Kies to flash this update, go read another guide to check how to do that, too lazy to post a step by step guide