It's as simple as going into the BIOS and raising the CPU multiplier. CPU clock speed is determined by a base clock of 200 x CPU multiplier so at default the 9850 has a multiplier of 12.5. 12.5 x 200 equals 2500mhz which equals 2.5Ghz. As you increase the multiplier you need to test stability and temperature using programs such as Prime95(stress test), CPUz(monitor clock speeds), HWmonitor(watch temps). If you come back unstable increase CPU core voltage, default is approximately 1.3V on there and I wouldn't go over 1.4V. You should be able to reach 3.0-3.2Ghz. Just be careful as the Phenoms are power hungry and run hot, I killed a motherboard trying to reach 3.1Ghz on a 9850 a couple years ago.
More information is here. http://www.tomshardware.com/forum/258573-29-black-edition-overclock-guide-raising-multiplier