Hi
In version 3.04 Use File/Record/Narrate.
This will bring up a Narration window with the Start/Stop and mike level monitor. If you think this is too small then click the Screen expand button in the top right hand corner. This gives an image about 75% the full screen size.....that should be large enough for most people. But full screen ....No is the short answer.
In version 2.41 you are stuck with the smaller Narration video window with no way to enlarge it.
Nat