Postpartum

Same way anyone else does: Eat fewer calories than you burn (all day, in every way from heartbeat/breathing to job and home chores to intentional exercise).

If you're breastfeeding, consider eating at estimated maintenance calories and letting the milk production create a small calorie deficit.

I started at 5'5" and 83kg. I wasn't breastfeeding, so I just went with a sensibly moderate calorie deficit, and reached a healthy weight in just a bit under a year. I've been at a healthy weight for around 8 years since. Calorie counting can work, if it suits your preferences.

Best wishes for success: The improved quality of life is worth the effort!

When my children were very young (3months and 2.5yrs), my gym offered child care so I took advantage of it. It was healthy and it gave me a break to be a person other than mom for an hour or so. I did not restrict my diet because I was nursing, but I did make healthier choices and snack less. I started lifting and cycling. I was way out of shape so my load was light and my rides were slow, but I did drop the weight. You've got this. It isn't a race, impatience and perfection are the enemies of progress.