In White, I wanna breed but it only gives me the option to put one pokemon at a time! WHY? EXPLAIN PLZ!
If you have only just reached the day care in your game, you can only put one Pokemon in there for now. When you get to Nimbasa City you help out the day care man and he goes back to the day care.
After that you can now put two Pokemon in there, and he will let you know when there is an egg, etc.