Set up the router in a convenient location so it's as close to devices that need to be connected to the router wirelessly as possible.
Make sure that wireless is enabled (you should find a wireless on/off button on the router panel - netgear dgn2200). Then from the wireless tab of the router config page, assign a SSID and save changes. Basically, you're good to go at this point but leaving the wireless network open and insecure is not a good idea.
Now with wireless network security, you have multiple options. There are numerous articles on this topic specifically but to save you the time; the most commonly used systems, specially for home networks are WEP and WPA2-PSK. You can use either but WPA2 has been proven to be a much more dependable pattern ever since introduced. I recommend that you use it instead of WEP.
I'm not going to get into the details one by one since you've asked a very general question and it would take hours.
If you have any specific questions about the wireless network settings, I'd be happy to help but as long as you need a basic wireless network, this should suffice.