I suspect that the Win8 driver for your wireless device isn't installed. At this point, you don't have much choice - you must find another computer with an internet connection.
Write down your Dell service-tag number - you'll need it for quicker access to Dell drivers. Then, find a computer that connects onto the Internet and go to the Dell Support website and type in your Service Tag Number. It should give you a list of drivers you can download and install. You'll probably want all of them - Motherboard Chipset (which may include video), LAN, Wireless and all the others. Download those, load them onto a USB memory stick and insert that back into your Dell and install those, one by one.
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The Win8 Reinstall only installs the base level Win8 operating system. Every manufacturer might install the unique computer models drivers onto it, or they might not, leaving that up to the end-user - you. Your LAN port (the Ethernet port) might not even be activated at this point - not without a driver!
So you'll probably save some time by finding a friend's computer with an internet connection. Take that Dell Service Tag with you - that's a time-saver. And a USB memory stick. 4Gb should be enough, but 8 or 16Gb definitely will be.
(I also recommend snagging a 14- or 25-foot ethernet cable - called Cat5, or better yet, Cat5e or Cat 6 - for any later use. Those will always provide a faster Internet link than Wireless.)