Use MSI Afterburner then test stability and do benchmarks with furmark.
MSI Afterburner Downloadhttp://downloads.guru3d.com/MSI-AfterBurner-download-2392.html
Very easy interface pretty fool proof has fan control and can save different profiles its a great tool and dont worry it works no matter which brand GPU you have it doesn't have to be MSI card for this to work.
Furmark benchmarking and stability test tool.http://www.ozone3d.net/benchmarks/fur/
Remember keep an eye on temps while overclocking also do it in small increments just dont ramp it up as high as it can go you could damage your card by doing that.