You may insert your cd to optical the drive before you turn on your laptop, if you automatically take you to Windows installation wizard.. If not you have to turn it on again and immediately press F12 to get in to bios to change boot sequence.
Does it have a previously installed OS? Try DELL recovery partition:
- Plug in your laptop using the power cord. Turn on the laptop. Watch for the blue bar at the top of the screen. Immediately press "Ctrl-F11" on your keyboard.
- Click "Restore" and "Confirm" to launch the recovery process. Once finished, reboot your laptop.
Dell sometime has the recovery option built into the Windows repair/recovery features at start up. If Ctrl + F11 does not work, try holding down F8, then select "Repair my computer" from the list. Once the recovery options are displayed, look for a factory recovery option.