Navigation through the 3D scene is done by maneuvering one the three different types of cameras.
Usually camera movement and rotation can be done by holding one of the mouse buttons: rotate by holding the right mouse button and moving the mouse; move the camera by holding the middle mouse button and moving the mouse.
This might sometimes not work when running Factory I/O on a virtual machine or remote desktop. To fix the issue, type the following command into the console:
input.force_alternative_mouse_data = 1
To learn more about console commands visit the console documentation page.