The outer bobbin cover has a spring-loaded latch on the side toward the back of the machine. That will release the cover, but it doesn't come off, it just drops out of the way. The bobbin case can then be accessed. That's a very small space allowed to access the bobbin. Be very careful with the bobbin case; it appears more fragile than most, and is basically unobtainium.
Congratulations, your machine looks very nice. Mine, identical in appearance except the decals and name, is the later General Electric. It sews nicely, but is certainly a heavy little thing!
Dianne