When NeuTu is launched, the home window will be displayed first and then an empty proofreading window will be opened in the front. You can use the native window system of your operating system to bring the home window to the front, or use the Advanced -> Show NeuTu Desktop menu to do it.
This window is mainly used for launching a new proofreading window.
It can also be used to open a TIF file, a SWC file or a mesh obj file directly. Just drag and drop a file into the window.