Increase this setting gradually, boot the PC, run it for a bit and repeat the process until you find a setting that’s unstable and causes the PC to crash. Record it somewhere, reboot into the BIOS and set the RAM clock to the last stable speed.
IMPORTANT: Read the following
RAM works on a standard of 1.5v. Making the memory work faster means it’s also going to need more power. However, that power need is tiny, so any increases should be done in .1v increments. Never take the voltage over 2.8v. If you rush this bit you risk frying your memory and rendering it useless, so be careful.
Go to the “Memory voltage" setting if you have one and slowly increase it. Some motherboards will have infinite options, others will have a set few. Whichever you have, choose the smallest change each time and test it. The test is exactly the same as before, run the machine for a while to ensure stability and find the voltage that works.
Once the system starts crashing again, move the voltage down to the last stable one and run the system for a few hours with these new settings. Tax the system, run games, benchmarks, whatever to make sure your memory is stable.
That’s how to overclock your RAM in a nutshell. You can also increase your CAS latency timings, but this can sometimes have the opposite effect and slow things down, so it isn’t always worth the hassle.