First of all, stay away from any "combination Cleaner/Conditioner". The most respected product on the market is LEXOL. I have used their cleaner and conditioners for my last 4 vehicles and have always had great looking and feeling leather - ALWAYS, LIKE NEW..
If you've never treated your seats before, wash them as directed with the cleaner and then very generously apply the conditioner. After a couple of hours wipe down with a clean towel and reapply another shot of condtioner. YOU WILL BE AMAZED!l