Join a gym and start eating right. Its important that you realize everything takes more time to happen when you are older.
Start lifting and get yourself walking, then start lifting more and walking longer distances, then distances with a pack on your shoulders.
You wont see your 20's again, but months down the line you will see improvements that will amaze you.
Just don't expect to see it happen overnight or you will be disheartened and quit.
I found it helpful to have very specific reasons in my mind when I workout. I don't listen to music, I keep my mind focused on why I am doing it-
stay the course.

The only power any government has is the power to crack down on criminals. Well, when there aren't enough criminals, one makes them. One declares so many things to be a crime that it becomes impossible for men to live without breaking laws.