Your computer, upon booting up, will tell you which key to press to enter Setup, the file that tells the PC how to configure itself.
The key is divulged in a short message that appears at the bottom of the screen as the bootup process begins and before the Windows splash screen appears.
The message usually reads something like "To enter setup press" and the name of the appropriate key. If your computer does not give you the instruction, you will have to experiment.
Try the Esc, Del, F2 or F10 keys. If none works, call the manufacturer of the computer.
Setup, which actually gives you access to the BIOS file, is divided into several sections, each dealing with a specific part of your computer and its hardware. Each section is divided into additional subsections. By the time you have worked your way through every corner of the BIOS, you will have been given the opportunity to make dozens of adjustments, from resetting the time to determining which USB ports are active.
There two basic warnings about dealing with the BIOS. If you change something, move carefully, ensuring that you are changing the setting you want. Also, never make a change without first writing down the particulars of the setting. That way you know what to change back to, if necessary. An excellent source for learning about the BIOS file can be found at http://www.pcguide.com/ref/mbsys/bios