For varicose veins, he will need to use stockings for support
He needs to start with calf strengthening exercises. You will need help of physiotherapist or an occupational therapist who can help him with the exercises.
Next Steps
Also, you need to get USG Doppler study of lower limbs - Venous to understand the severity of the problem.
If the problem is severe, consult a general surgeon or vascular surgeon who is dealing with these problems..