It is hard to be alone -alone in your own head -all the time. I have been sitting here in the house all day (due to sinus infection) drinking tea and puttering around. I'm ok with that because I am not lonely -just alone. When I am lonely I go shopping! LOL
But seriously, when my youngest started pre-school (15 years now?) I volunteered tutor at the elementary school where my other two were. Nothing major. Just listening to kids read or helping with homework that wasn't finished. But I got to associate with adults -parents and teachers and volunteered at all the 'fun stuff'.
Do you have a community center in your town? How about volunteer for kids' sports. They are always looking for people to help coach, etc. What about a local animal shelter? They often need people to help at 'adoption days'.
Hospitals sometimes look for people to volunteer.
The 4H program also need adults to help with their kids. I volunteer in the summer to judge chickens/rabbits/cats in two counties. Its out there...