If you need to give your friend access to your WiFi you can usually find it by going into your network icon in the systems tray, right clicking on the WiFi you're connected to going to properties and then the security tab in the new window, check show password and you'll see your password.
If you're trying to share a folder with your friend (without using the homegroup) the username and password would be the one you use to login to your computer (I recommend you create a new user account specifically for sharing in this case).
If you're trying to set him up on the homegroup you need to give him the password which can be found by going to control panel and typing in homegroup. In here click view homegroup password and give that to him.