I started doing this back in the mid `80s in Los Angeles because I was stressed something awful. I can say it does work for me and I noticed it right away. That was long before I heard about shinrin-yoku.
When I started doing this I would look for a good place with lots of trees and fresh air, a creek or stream was always good, and I'd pack a small day bag with water and some snacks, a beer and a bud, and go meander around. I'd find a secluded spot to sit and relax for a spell and maybe explore some more or just stay put and soak it in. If you sit still for awhile the forest critters start coming out and doing what they do and it can be a pretty relaxing thing to just sit there and do nothing but observe that.
Here's a link to an article about shinrin-yoku. I'm sure there are quite a few articles about it to be found and I just picked one that seemed to fit the bill. Some of them I've read include some reasoning for how and why this works. All I can say is it worked for me and still does: https://www.rei.com/blog/hike/theres-no-running-in-forest-ba...