to oc your gpu
step one: increase the gpu clock speed in large jumps at first until you see artifacts then slowly decrease the clock speed until their a no longer artifacts.
step two: If you still want to oc more increase the voltage a small amount and repeat step one (repeat).
step three: To over clock the memory do the same thing you did before but with the memory instead of the gpu core itself.
you will need msi after burner(will work with non msi cards) or any other gpu over clocking software
each time you change a setting you should run a stress test to see if it is stable