It sounds like you have the desktop plugged directly into the modem and now you want to install a separate router so you can share your internet connection with other computers (laptop). What I am providing below is based on that assumption.
I tried to do it graphically but it won't paste in here. So, see below, you have the modem which is attached to the wall by the Coaxial cable (for Cable) or phone line (for DSL), then the modem connects to the router by LAN cable, and then the router is connected to the desktop and laptop by LAN cable as well.... that is unless you setup the wireless connection so the laptop can connect wirelessly. Try to get the desktop working before trying to play with the wireless though, then at least you know you the router is working with your internet connection.
Wall ------- Modem -------- Router--------- Desktop/Laptop
I always unplug everything on the router and modem, including the coaxial cable or phone line on the modem, and let it sit for a couple minutes. Then I plug the coaxial cable/phone line and power cable to the modem, let it power up for a couple minutes, then I plug the power into the router and let it power up for a couple minutes, then I plug the LAN cable from the modem into the router, and then finally I plug the other computers into the router.
Note that most routers will have a port on the back that is marked as internet, this is where the LAN cable from the modem goes. The computers LAN cables get plugged into the ports marked LAN. If you provide your router model I can see what the back of yours looks like and tell you for sure what to plug into.
Hope this helps!
Hi,im having trouble (i am not computer savvy either lol) connecting up a laptop through my netgear router.I have a desktop already running through the modem.Can anybody help me by drawing me a laymans term diagram please (i seem better at using diagrams than instructions lol).Thankyou for your time and help 
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