the wi fi key is a key generated so that only people who have the key can log on
In the router in the wireless setup area is a wireless security area.
The wireless security is turned on.
( The most common form is wep 64 bits , then a more secure format called wpa)
You can either make a code to fill the requirements of the format or in that area will be a passphrase code generator.
Select it put in the phrase of your choice. It will generate the code.
When you go to logon the wireless connection the windows wireless utility will ask for the code ( you enter it twice like a password)
If you are having troubles logging on just turn off ( disable ) the wireless security in the router until you are more familiar with wi fi. No shortage of open wireless routers to find.
If you still have trouble and cannot get into your neighbour's wireless network people usually write the wep key somewhere around the computer
common phrases to guess are :
wife name
kids name
address
dog or pet
car model or make
http://www.andrewscompanies.com/tools/wep.asp