Hello @fnhc,
If you would like to display a message using a static block on a specific category, please navigate to the Dashboard > Static Blocks > All Static Blocks.
From there, you can copy the shortcode of the specific block and then edit the specific category from the Dashboard > Products > Categories. Paste the shortcode in the Description box and save the settings, please refer to this screenshot: https://postimg.cc/mcTxFH3k
Best Regards,
8Theme’s Team