Probably a rookie camera question

This is my viewport.

The camera renders the little tiny orange/red box. How do I make it render a larger portion of the screen? I don’t mean change the focal length or view angle. I want the box to be a larger portion of my screen because, for the moment at least, the rest is just dead workspace.

Cheers!

Homekey on keyboard to fit camera view to screen.
or Ctrl+MMB drag to make larger/smaller and Shift+MMB to drag position (ensure you have ‘Lock Camera to View’ disabled in Properties Panel)

Perfect! Thank you very much.