Depends on how you’re actually connected over there.
If the laptop is connected to a wireless router, then you connect the desktop to the laptop over wire and bridge the laptop’s wireless and wired connections using Network Connections (Windows key + R, type "ncpa.cpl" (no quotes) and hit enter, select the network connections/adapters, right click, select Bridge Connections).
If the laptop is connected directly to a wireless ISP (i.e., no router), then enable ICS on the wireless connection and share it w/ the wired connection.