CAT12 is not available in the compiled version of Brainstorm, which you are apparently running.
If you have Matlab installed on your computer, run Brainstorm from Matlab instead of the compiled packaged.
If you don't then you need to find information on how to run the compiled version of CAT12 on your computer, run it on the MRI, then import the output in your Brainstorm database with the menu "Import anatomy folder", just like in the introduction tutorials.