Social groups. If they're physically capable, get him or her involved in social groups for the elderly, many of which you could find in your community through your city/township or the church/synagogue. If they're more debilitated and limited, lots of socialization can be found in an assisted living facility or even a nursing home.
Social health. Check out http://study.com/academy/lesson/what-is-social-health-definition-examples.html. 1st look to family to engaged w/elders. Consider using them as resource to learn about family history. 2nd look to community to find like-minded individuals eg similar hobbies, vocations, interests, etc. Consider volunteering at art & science museums and at schools. Religious institutions can provide options.