I had a really good question on our Ravelry group about pockets! Pockets are something that is inherently scary with knitting. There are a lot of fears around putting them in and the stretching that could happen. I wouldn’t suggest carrying anything too heavy in them.
There are quite a few videos out there and I picked these three, but if you’re not able to get what you want from these, just search pockets in knitting. There will be a lot of information that comes up!
I’ve got three videos about how to put in pockets, but the placement is important too. There are generally instructions about pocket placement, but if you’re looking to place them yourself I would add the pocket in after the garment is finished. That way you can look at where it would make sense to have pockets.