Unroll the Camera section tab.
By default Camera Type is Perspective. You can change it to any orthographic projection to make the align process very easy.
Because of some limitations of OFX plugins we can’t use Nuke’s Cameras directly. But we can connect it with expressions:
Create 3D Camera
Open both properties of 3D Camera and GS Camera in the Properties panel.
Hold Ctrl (Cmd) and drag Camera Translation, Rotation, Pivot, Focal Length, Horizontal and Vertical Aperture as shown on video below: