Hello, not sure to understand your question, so re-formulating it:
You installed CB Activity and CB Gallery, but don't see gallery posts on the wall ?
Have you also installed and published the CB Auto-Actions plugin, and also published all CB joomla plugins ?
It's in Joomla's Extensions/plugins then search for "CB" and make sure their status is Enabled (green checkmark).
That will not show existing gallery items, but should show newly uploaded ones.