I've just started a measured walk everyday, with a view to extending (gently) the distance as I go.I walk with a stick due to a bad hip and can only go shockingly short distances.
Luckily there is a dog walking park next door, with a paved track around it. So my first day was to the park entrance n back. Then another hundred yards or so n back etc.
I will use the pedometer on my phone, to semi accurately judge my progress, until I can do a full circuit, then try for a circuit n a half etc etc.
I'm on a diet (and losing) and do simple stretching exercises daily to improve joint mobility.
The first steps are the difficult ones, making yourself do this.