How do i stop wireless people around me from conn.throu my internet an slowing mine down?

As the others said, you'll need to setup security on the router. You'll need the IP address to access the router with your browser, and then the login and password. Try googling the brand name and the words "default IP address" and enter that address in the address bar in your web browser. Do the same thing for the username and password, google default username and password and your router type. Then you can login and enable security.