How do I rename the Wireless network and password on my PC?

Windows 7 Ultimate x64
Home Network

How to I rename the Wireless network and password on my PC.
Will doing so prevent other people from connecting to it even though their computers were at one time allowed to. I have had some neighbors computers in my apartment and connected them to my network to see if I could help them figure out why their connection wasn't working. I know they can see my wireless network because I can see theirs. How can I make sure they can't actually connect to mine?
And if I do rename it will I have to make changes to all my devices and other computer or will that happen automatically?

You need to change the password at the router, not at the computer. Use its web interface and in its security section you'll find an option to change the wireless password (details on how to do so are specific to each model). Be sure to use a strong, random password instead of an easily guessable one.

Then yes, as you say, you'll need to change that same password on each device that connects to the network. Once you change the password on the router everything else will fail to connect (saying "wrong password"), including your neighbor. Just go to each device and input the new password and they'll work again.

Changing the network name is not necessary and it doesn't adds security. SSIDs are public anyway, and it doesn't matters is anyone knows them as long as its password is keep secret.