I have a question to do with building an Augmented Reality app using JPCT (and OpenCV) which places graphics over planar book covers.

Imagine this scenario.

I have a planar rectangle in my scene. The center of the rectangle is at world coordinate (0,0,0).

I have used OpenCV solvePNP to get a 4x4 Matrix containing a transformation (comprised of a translation and a rotation) from the world/model's coordinate system (they are the same) to where the camera should be placed.

My question is:
Where should my camera initially be placed and pointed in the world coordinate system and...
How should I then apply the 4x4 transformation to move and reorient the camera from its initial position and orientation so that it is in its the right position and orientation?

I should add that I am just rendering a primitive sphere at the origin for now.

Let me know if I should clarify! (I am a graphics novice)
Thanks in advance
Oli