The user name and password for the router might not be the same as that for the PC, so you will have to ask your friend what this is or have him call the ISP if he got the router from the ISP.
To configure the wireless settings for the router, you must type the LAN IP address for the router in your Web browser. To find the IP address for the router, you can check the IP configuration of your friend's PC (i'm assuming, here, that his PC is already successfully using the router as it's gateway to the Internet):
1. On your friend's PC, click Start > Run.
2. Enter cmd and click OK
3. Type ipconfig and press Enter
4. The group of four numbers next to the words Default Gateway is the router's IP address
5. Open the Web browser on your friend's PC and type that number (with the periods between the numbers) in the address box of the browser and click Go.
6. A page will be displayed in the router where you must enter the user name and password. The default settings for some routers are Administrator for the user name and Password for the password.
If you get that far, find the option to set the wireless security and set it to no security instead of WEP, or write down the encryption key (which will be several letters and numbers) and enter that in the wireless settings in Windows on your laptop. If you set it to no security, any laptop or other wireless device will be able to use his router to get to the Internet and possibly get into your laptop or his PC.