I would simply instatiate the camera class in the base game class so that you can easily set the Matrix in the spriteBatch overload.
When you then initialize other components, which should be able to manipulate the camera, then just give those components the reference of the camera instance per overload in the corresponding constructor.
If this doesn’t solve your problem then please open a new topic and describe your problem there. You should do this for every new question / problem you have, because it could be also relevant for other users and it becomes easier to find solutions for problems in that way.
Thank you 
