By taking exercise. It doesn't have to be exercise specifically for keeping fit,. It can be housework, gardening, dancing, sports, walking, swimming, etc.
I have a tall house, with 3 flights of stairs. I try to climb to the top at least 10 times a day. Sometimes, I manage 20 full climbs.
My laundry is dried on the solar powered machine - i.e. I hang it on the washing line. That gives me some weight lifting exercise and some stretching.
If you want exercises, the very best of all are squats. You can also walk / jog, swim.