Use init.coffee to set a window's position and size

In my tree view: Screenshot%20from%202019-06-02%2021-26-45
I want that right pane to be here in my tree view, but it resets to the first one each time I restart atom.
https://imgur.com/u5K2i9Q
I also want to set the height of the pane to be a certain number of pixels high, if that is possible. Even better, if I can represent it as a ratio.