{ 1 } - it's in everyone's self-interest to promote an atmosphere in which it's in no one's self-interest to violate morality.
{ 2 } - we're motivated to do the right thing for its own sake.
{ 3 } - we're altruistic and hence motivated to promote the good of others.

Hobbes sees us as egoists. But egoists will make life miserable for each other unless they set up moral rules. So self-interest leads us to promote morality and an atmosphere in which people who violate morality suffer external sanctions (alienation from others, social disapproval, legal penalties) and internal sanctions (guilt, anxiety, loss of self-respect). This explains why it's in our self-interest to be moral.