Hi Trish,
I put on loads of weight during HT. Only way to lose it again post-treatment, in my experience, is to eat less. Exercise improves your fitness, but it's virtually impossible to lose meaningful amounts of weight simply through exercise.
I found that what worked for me was an intermittent fasting diet. Two days a week I skip breakfast and lunch and restrict dinner to 500 kcal. Other days I eat normally. I can lose a steady 1kg/week this way.
Cheers,
Chris