User blog comment:Theorempswenel100/DnSpy help request/@comment-30175469-20190329140256

Well first off you don't want to place it in the slime rancher folder, that is likely placing a game folder inside another game folder.

Second, you want to extract the zip file, once extracted just open the new folder and run the application. From there, file open the assembly found in the slime rancher folder