The phrase "to socialize the cats" means to help the cats become more comfortable and friendly with humans and other animals so that they can interact in a more positive way. Full definition
By opening your home to these pets, you can help socialize a cat who has not had as much exposure to a loving human family. (animalbehaviorcollege.com)
They wanted people to help socialize their cats, to help the cats become more adoptable, more accustomed to different people. (catdepot.org)
Sometimes people ask how long it takes to get an under - socialized cat ready for adoption. (cattownoakland.org)