Generally, the only wires that are relevent are the wires that were on the old device (switch/outlet combo).
If you are referring to a catalog number 7299 (diagram below), take note that on the back of the device there is a top and bottom, one says "line" one says "load". We will only be using the line.
Hot wire from your panel, goes to the line hot terminal, brass screw
Black lead from the 7299 (doesn't matter which one) also goes to the line hot terminal
Neutral from panel goes onto the line neutral terminal (silver screw) on 7299
If there is a neutral from the device (light/fan) you wish to control with the switch of the 7299, also attach it to the line neutral terminal of the 7299
Take the remaining black lead hanging from the back of the 7299 and attach it to the wire that carries power to the device (ligh/fan) that you wish to have controlled by the switch on the 7299.
Thats it. You may need to press the "reset" button once the breaker is turned back on.