• Left Mouse Button (LMB): move mouse to change camera angle around shape.
• Mouse Wheel: zooms in and out.
• CTRL + LMB on shape: selects the closest vertex to the clicked position.
  • LMB on x,y,z-axis: move mouse in screen's x,y-direction to move vertex along selected axis.
• CTRL + LMB on background: removes the selection again.
• SHIFT + LMB on shape: selects the closest landmark to the clicked position.

For more information, especially about the control panel on the right, click here.