New to breastfeeding and just ordered these

I just ordered these and wondering should I wear them when I’m out from the house? Like taking my other child to school/ grocery shopping? Or just wear my pads....

I do know I was planning to wear one while I feed and pump

Also

What is the best way for me to get my milk flow going very good?

And will I lose weight or gain weight?

I’m hoping to gain I know you have to eat a lot of calories but how can I try to avoid from losing as some people told me they lost alot of weight