The order you add categories, clients, and banners matters, so use this order.
Go to Components>>Banners>>Categories
Select New
Enter all information you feel is necessary for the general category then save
Go to Clients and select New
Enter applicable information about the client then Save and Close
Go to Banners and select New
Enter applicable information about the client
Under the Details tab
- Name the banner
- ensure the category you created for this banner is selected
- select an image for the banner and adjust dimensions as needed
- Add click URL
Under the Banner Details tab
- Select the client you created for this baner
Save and Close