Hold the left mouse button and drag the mouse to rotate the shape, use the right mouse button to pan the shape. Use mouse wheel to zoom the shape. Touch gestures are also supported. Click Zoom button if you lost.
The toolbar at the top lets you control the 3D preview and setup the scene the way you want it to be rendered:
When you click Render you will need to select the quality of the rendering. The higher the quality, the longer it takes to render the image.