Everyone have a way of socializing. No matter how difficult, unsocial some might seems. Study them when they are not in their cells, look out for what interest them most. See the kind of areas they play towards. Look out for likes, you should find those that relate well in same way. Create an environment where like minds can rob heads and participate in one activity. With time when they familiarize with each other, the can come to like each other and socialize.
Each of them have one reason or the other that must have brought them in the prison. It doesn't mean they cannot socialize. They just need like minds to associate with.
One thing that I have seen that is beneficial for inmates is mindful communication. It helps people reduce the time between an angry emotion and reacting and also with communicating with people in general. Below is a citation for a book on the topic. It may need cultural adaptions.
All the best,
Nikki
Huston D, 2010, Communicating mindfully: mindfulness-based communication and emotional intelligence, Cengage Learning, New York.