How do you add air to the rear suspension shocks on a 1996 Harley Davidson FLH Electra Glide Classic also what is the proper tire pressure?

Simply follow the nylon air hoses from the shock absorbers and you'll find the air fitting, which is the same size as a tire valve stem. Use a hand pump to add air, otherwise you risk blowing the shocks' seals.

Recommendations for tire air pressures vary on different brands and sizes of tires, but every tire made, regardless of application, has that information printed on the sidewall.