How to open VIEWFINDER in Life is Strange: Before the Storm (Episode 1)
Once you jump out of the train with Rachel, Chloe hast to find a way to pry open the viewfinder on the hill with a specific tool. .
First you need to inspect the viewfinder and than interact with it after that. Chloe suggests that Rachel might have something that could help out.
Take Rachels Nail File and to the second bench on the right. You can unscrew the plate there and use it on the viewfinder.