Assuming that you don't know anything about OC'ing, some definitions are in order:
Clock speed and Multiplier
determine the speed of a piece of hardware. Think of data as water. To find the speed of the "water" in any given component, multiply the clock speed by the multiplier. Most OC'ing is done by changing the clock speed, but certain applications can change the multiplier as well (e.g. TurboV Evo). An "unlocked" processor (e.g. Intel's k series or AMD Black Edition CPUs) does not have any upper limit to its multiplier (most processors have a fixed multiplier that cannot be changed). Lag is created when too much "water" is being pumped into the components, building up pressure. Unlike water, data does not move faster when there is more of it, so pressure builds up inside the system.
Threads and Pipelines
Using the water analogy, threads and pipelines are like the hoses that supply components with "water." More hoses and/or bigger hoses allow for more "water" and less pressure. The speed of a thread or pipeline is like the diameter of the hose.
The amount of electrical power that is supplying a component. In general, increasing the speed of a component requires increasing the voltage. However, DO NOT
manually increase the voltage unless you are 100% SURE that you know what you are doing. Setting improper voltages can completely fry your system. I suggest letting an OC utility take care of voltage adjustment for you.
That's pretty much all the basic definitions that you need to know. Now, for the OC part. There are two ways to OC your computer. You can either use BIOS or a utility software. I recommend using an OC utility as it's easier to adjust the settings, changes can usually be reversed if your computer becomes unstable, and most utilities offer automatic tuning. If I'm not mistaken, You're running a 940 BE and a Gygabyte mobo. I can't help you with the BIOS- all of my experience is with ASUS mobos. Because you're using an AMD CPU, you can run the AMD Overdrive Application (AOD) that is found here: Drivers & Support | GAME.AMD.COM
This is a good application, and is provided by AMD itself. Because you have a BE processor, you have a wider range of options for OC'ing.
As its name implies, overclocking is usually done by changing the clock speeds. Because you have a BE CPU, you can also OC through the multiplier. I do both.
Here's a basic tutorial for the AOD app.
Launch the app. Click yes to admin privileges, then you're going to get a warning message by AMD telling you that OCing can be dangerous (albeit in pages of unnecessary re-wording). Click yes, and after a short delay, AOD opens up. If it tells you to register or anything, do (or don't, shouldn't matter). Once you get to the main app, you should be on the "basic info" page. It can look really confusing, don't worry if it does. Eventually, you'll learn what all of those things mean through experience.
Click on the "performance control" tab on the top. The default preferences are novice mode, so you'll be brought to a simple-looking page with a sliding meter on the top and a chart of clock speeds, multipliers, etc. on the bottom. You should have something of an idea of what most of them mean by now. The easiest way to manual OC is to take the little slide on the meter and slide it over to the right. That's it. Make sure that you have a good HSF if you want to move it over past, say, two or three. If your computer crashes, restart the system and load default BIOS settings. As with any method, this will take much trial and error before you come up with the best settings.
Alternatively, you can auto-clock the system. From the novice mode tab, click on the lower tab on the right side that says "auto clock". Click on the start button and wait, the tuning process can take a while. If your computer crashes, no worries, reboot and load default BIOS settings. That's it.
Once you've OCd your system, it's probably a god idea to run a stress test. You may use your own or use the one provided by the AOD application (it's one of the lower tabs under "performance control" section). If the temps are too high for your comfort, or if the computer crashes, then reboot and turn it down a little bit. It's all trial and error.
Long guide, but hopefully this helps.