Parallels like other virtualization software for Macs uses a virtualized hardware layer. This layer doesn't have direct access to the real hardware (Type-2 Hypervisor). This includes the Wi-Fi-interface.
Instead software ethernet bridges are used to access the hardware indirectly. That's the reason for the network interfaces of the Mac (e.g. en0: ethernet, en1: wifi) showing up as ethernet interfaces in the virtual machines.
Consequently Windows 8 or any other OS running in a VM on a Mac can't show and access any Mac internal Wi-Fi in their network settings.
There might be one exception:
USB-Wi-Fi sticks directly attached to the virtual machine. I can't verify that since i don't have such a stick. Hint