You have a nice GPU.
You can download a program like MSI Afterburner to aid in OC'ing your GPU.
OC'ing is a process of incrementally increasing the various things pertaining to your hardware.
Things like voltages for example.
I advise you to do some more reading on OC'ing if you haven't. If you do it wrong, you risk breaking your system.
Also, OC'ing won't necessarily give you any kind of substantial performance increase, while reducing the life-span
Of your hardware.