To root your device, you will need software that has that functionality. You can use Google in order to find one. I suggest you try UnLock Root. Before you start this process you get to make sure that you have installed the appropriate driver for your device. Usually you can find this on the official manufacturer's website. Also, you need to be sure that USB Debbuging mode is active on your device. To do that, you need to go to Settings -> Application -> Development. After that, connect your device to the computer and start the software. You need to wait until the software recognizes your device, select it from the list, click the Root button and wait. After this process is finished, just restart your device for the settings to take effect.
I highly recommend before you start the rooting process to back up your data from the device.