A Banner belongs to a Banner Group, as assigned by you in the Banner Manager ...
You can use an existing Banner Group, or type in a new name for it ...
As you add Banners to a Banner Group, you will notice the next time that the Banner Group will appear in the dropdown ...
The dropdown is self learning ...
Then, in the Configuration ... Layout Settings ...
There are 8 places where you can add "what" Banner Group should be assigned to which banner location on your shop ...
This can be 1 Banner Group to many Banner Groups ...
Leaving the setting Blank turns OFF the Banner ...
So, if you add a new Banner to a Banner Group called: MyStuff
... but never add the Banner Group name: MyStuff to any of the Layout Settings for the Banner Groups ... you will never see the new Banner you added in the Banner Manager ...
The 9th Banner Group in the Layout Settings ... is for Banners All ...
This is a special Banner box that shows multiple banners at the same time in the order that you assign in the Banner Manager ...
Something I often recommend to everyone is to install a test directory with a test database with the demo products so that you can test all of the features in Zen Cart and really see how they work ...