Final answer:
The nurse should advise the client to walk 15-20 minutes 3x a day.
Step-by-step explanation:
The nurse should teach the client diagnosed with varicose veins who has received sclerotherapy to walk 15-20 minutes 3x a day. This is because walking can help improve circulation and prevent blood from pooling in the legs. Additionally, walking can help strengthen the calf muscles, which helps in pushing blood back up towards the heart.