Given your description, I guess you computed the source directly for the continuous (=raw file).
This option of computing full source files (instead of the optimized format with the imaging kernel) is only available only for imported data, and not continuous files, indeed. Same thing for the "model evaluation" menu.
For the difference between "imported" and "continuous/raw", see the introduction tutorials:
https://neuroimage.usc.edu/brainstorm/Tutorials/ChannelFile#Review_vs_Import
If you are a new user of Brainstorm, I recommend you start by following all the introduction tutorials (section "Get started"), in the correct order, and using the example dataset provided, not your own data.
https://neuroimage.usc.edu/brainstorm/Tutorials
If you are interested in processing EEG or resting state data, read the two additional tutorials:
https://neuroimage.usc.edu/brainstorm/Tutorials/Epilepsy
https://neuroimage.usc.edu/brainstorm/Tutorials/RestingOmega