Buy a wireless Access Point and plug it into the NB5PLUS4. I like Netgear or Cisco. Cisco is a bit pricey for most home users, but a Netgear WPN802 goes for around $80 USD.
Alternately, if your ISP can provide you with a replacement like the NB5PLUS4W, the W meaning it has wireless, that would be your best bet. Many providers will provide you with a free swap to a wireless router from a wired-only model. It's best to just let your ISP give you a router, then there are no issues when something breaks.
Once you have the WLAN router or Access Point, the next step is to add WLAN to your desktop. Either a PCI WLAN adapter, like the Netgear WPN311 or a USB adapter like the Netgear WG111.
Here my recommendation is that a PCI adapter will be more work to install, but will work better and more reliably. USB seems to be a less perfect way to connect to the network, and you use up one of your USB ports.