Realizzer uses an Orbit-Camera which is always "orbiting" (rotating) around the selected object.
Use the left mouse button to rotate the Camera around Y and X Axis.
Use the right mouse button to move the camera position in view space.
Use the mouse wheel to Zoom in & out from current view position.
By holding the CTRL- or Shift-Key on your Keyboard you can change the move speed to slow or fast.