There's no automatic integration with Joomla articles. The CB Gallery Bot usage would require you to insert a shortcode into each article. If you want automatic integration you might be able to do that using CB Auto Actions and a Gallery action acting on joomla_onContentAfterDisplay to insert a gallery. This is how CB Activity for example adds comments/likes to articles. Something like the below (quick example! not tested!):

Global
Triggers: joomla_onContentAfterDisplay
Type: Gallery
User: Specific
Specific User: [var2_created_by]
Conditions
Field: Custom > Value
Custom Value: [var1]
Operator: Equal To
Value: com_content.article
Action
Mode: Gallery
Asset: article.[var2_id]
Output
Display: Return

Likely will need adjustments, but should be a good starting point.

Thank you for the instructions. I have tried all the available tutorials from the discussion forum here (comments on the article, code for non-registered etc.) but without success. Just set the automatic actions and everything happens automatically? Or do I need to enable something somewhere?

Does the above output nothing? Try removing the condition and see what happens as you might need to adjust what context you're trying to display it on.

BTW, I have a feeling that in previous versions of CB there were maybe 90 predefined automatic actions (Activity logs, Groupjive..). Now only two auto actions.

Those were for CB Activity integration. With CB Activity 6.0.0 they're no longer needed since activity and notification logging is just built into CB Activity. This means those system actions are now removed.

Was able to confirm it's not working due to changes to Joomla 5 content event. Have implemented a fix in latest CB Auto Actions build release and confirmed it's now possible to output to the newer Joomla event objects.