What do you like doing? Find yourself a group that also enjoys such things.
Go join an amateur dramatics group, join a choir, take dancing lessons, learn to horse ride or learn first aid, or take up diving again.
Join a book club, a local charity, a local political group and make friends and acquaintances.
Join a dining club, a singles group, a walking / biking group.
Volunteer at a local charity shop, or hospice, or hospital.
Loads of things to do that involve meeting and mingling. People very definitely need the random brownian motion of interacting with others :)