I combine aseg with cortex and obtain a whole brain
Extract only the cerebellum, if you are interested only with the cerebellum.
Since it looks like you are working with an anatomy template: download the ICBM152_2019 full template (right-click on the anatomy folder > Use template > MNI > ...), it includes a surface with cortex+cerebellum.
Then I compute headmodel, covariance matrix and source for mri volume option. Here I see I think is where we add volume scouts from atlas. I can do that but I already have a source model where almost there is activation for each time in the whole brain.
Create a volume atlas, create a few scouts, make sure you can do what you want with these scouts.
As a second step, you may try to import a MNI template as an atlas (in MNI space, therefore not from fsaverage).
We've added the automatic download for many MNI templates in Brainstorm, but we can't use them yet as volume atlases. Coming soon...
About fsaverage I didn't meant to use it as template but I use parcellations from those files in fsaverage. If not where from I can obtain aseg+aparc files? From a segmentation with recon-all that is computing freesurfer over IBCM152 template.
Exactly.
This will be available in a few weeks (or months) easily in Brainstorm. But for now, you need to process the volume yourself.
If you want to use the FreeSurfer Destrieux or DK/DKT40 atlases, I'd recommend you use the surface version (and therefore a surface head volume) - then they are already available in the cortex surfaces of the template.
Also I want to mention that when I use ay atlas from spm to scouts I ony see numbers and not the names of those scouts. Is there something I am missing?
The volume parcellations you import contain only integers. These are the values you see.
We are in the process of adding default labels for some atlases, but this is not finished yet.