First go in admin > system > design > banners , and there you either edit or insert banners.
When you clicked insert (or edit) you will be taken to the banner page. In that page you have to insert more images
by clicking "Add banner" if then you want a slideshow.
Upload ad banners created in a graphics program, give them a title and link to a URL.
NOTE: Must also turn on the banners and specify where to display them in Extensions -> Modules -> Banner.
Status
Select Enabled to allow ad to display or Disabled to hide.
Title
Give the ad a name that is easy to remember when you view it in the Admin.
Link
The exact URL where you want the customer to go when they click the ad banner.
Image
Click the photo to bring up the Image Manager and select the ad banner from your computer.
Click the Save button to upload and save.