I presume what you have got is a DELL OEM Reinstall Disk. It should install and self-activate offline
preserving the OEM activation. Please download all drivers
or atleast the network drivers for your system from the DELL support site so that you can go online and update. ( If it is an OEM Reinstall Disk it will not have any drivers in it. I always prefer to download all drivers from the manufacturer's website for the first install.)
Please do make a backup copy of the install media and keep it safely for future use - in case you lose the media or the media gets damaged.