Well you just insert your Win 7 DVD & restart the PC. At the BIOS page, press the suitable button to boot from DVD. At the install page, you then get the options for formatting, deleting/creating new partitions, etc.
You will of course need the DVD or USB drive setup with Windows 7 install package. At that point setup your BIOS to boot to DVD or USB depends on the media setup.
The Windows 7 install process will then begin. All applications and documents stored in other locations will have to be reinstalled / transferred manually.
For more information on the Windows 7 Upgrade, please go here: http://bit.ly/3DvynK
You won't need to change any BIOS settings. Just use the F8 key when you power on. Keep pressing the F8 key till you see the Boot Options menu on your screen and choose the CD option to do a 1-time boot from your CD/DVD drive.