You only need 4 of the bungs. The other two are just extras. Most people use them for EGT or aftermarket wide band O2 sensors.
Pre-cat O2 sensors go at the bottom of the headers. most people install them in the first set of bungs. Make sure you keep banks 1 and 2 sorted out correctly or the car will have serious performance issues.
Post-cat O2 sensors go after your cats. With the supersprint exhaust (assuming you bought cats), you will need to extend your post-cat O2 sensor wires. If you don't have cats, you can plug them in wherever you want or leave them unplugged. Either way you will have a CEL.