How do I change settings so that a friend at my home can use my internet connection with her wifi to go online?

I use Trend Micro and a while back they recommended that I change settings so that no one else could use my internet connection to access the internet but now I can't even use it without being hooked up directly.I don't remember what I did or how to change it back.Can anyone tell me how to do this ? I would like to have it to where we can both be on line at the same time when she is over here.Thanks.How do I change settings so that a friend at my home can use my internet connection with her wifi to go online?
Did you change something in Trend Micro or on your Wireless Router?

I'm guessing they suggested you secure your wireless network with a key(wireless passphrase) to connect to your wireless network. If you can't remember the key, just login to your router and copy the passphrase to a USB flash drive and then connect to your wireless network. Then when your friend comes over, click View available wireless networks, click on yours and copy the key from the flash drive and paste to connect.