Hai and welcome to KittyCatS
KittyCatS need to be 7 days old and have their breeding turned on, it is turned on by default so unless you turned it off you needn't worry about this. They will start gaining love at 7 days old and will gain 10% per day without Milk or Cuddles, 14% per day with Milk or Cuddles.
The stats needed for breeding are 100% love, at least 75% happiness, at least 25% energy (and be awake), and no more than 25% hunger. You can see more about breeding here in the manual.
http://kittycats.biz/help/
As for HOW to breed a good place to start is Saga Felix's documents which are located here https://docs.google.com/?tab=mo&authuser=0#folders/0B0_Wqb33nVpnZWYwNGViMGMtYWU4ZS00ZjAyLTk4OTctMzk2YzljODliMDhm
Good luck with your new addiction!