The blue screen typically occurs when something causes your system to become unstable. If it's the first time it has happened, turn your computer off by holding in the power button and then turn it back on.

If the error occurs again, write down what the error message says and post that information here so we can troubleshoot your problem. Also mention if it happens only when using a specific program or device.

Hopefully it was just a one-time error and your system will work normally once you reset it.