I meant first step is to do anything

because each person is unique and there is no one method for alls.
Start to do and every moment check Your feelings - You dont have to feel a pain and disharmony... it means, You control a treshold of pain and comfort. Do with pleasure

and feel a joy

))
Surya Namaskar will make Your body flexible, believe me. In the beginning strech a little and do it easy. After one week You will wonder about Your abilities

))))) I know good examples: old teacher (about 80) teaches others elders to practice SN and this gives a great benefit.