Measure the size of your basement window and purchase a lock that is properly sized for it. Look for a lock that is easy to operate from the inside of your home, yet impossible to access or tamper with from the outside.
Drill a hole in the center of the window frame. Insert the screw from the lock kit into the hole and tighten the lock down to the window frame.
Close the window and secure the lock. Test the window to make sure the lock holds securely.