ok can someone explain me how to keep one mob ?
If I'm understanding properly, you're referring to actually capturing things.
First, you need the right pen for the monster you're catching. Go up into town and talk to Cassie to build them.
(Warning, lots of meows. She's a Neko.)
Once you have the pen built (Vulwarg Kennel or Foxen House in the beginning) go to where you can catch the monster in question. There are two ways to catch monsters.
First, have sex with them and smash the left mouse button so that they coom but you don't.
Second is to buy the right kind of fluids from Amber-Mae or Camilla.
Milk can be bought from Amber-Mae, Semen from Camilla.
Male Vulwargs (Wulf) respond to Foxen Milk while Female and Futa (Lykos) respond to Titan Semen.
Male Foxen (Sionnach) respond to Bovaur Milk while Female and Futa (Vulpuss) respond to Vulwarg Semen.
Once you've satisfied the requirements (you only need to throw one load of fluids at them - much easier than smashing LMB), the Catch option should be available. They'll automagically be sent to the appropriate barn, if built.
If you meant how to get rid of everything but only keep one, "ascend" the ones you don't want to keep with the Emissary Seraph at the temple, or just release them from your barn. Sometimes there'll be Breeding Requests that you can use them to satisfy.
