The default banner set on the templates we use for the Template bundles are actually image galleries that are managed through the module manager.
Before starting you will need images pre prepared and of the right dimensions. Typically these images are 740 pixels wide by 250 pixels tall but the module can accept images of any dinension. We would recommend that all the images you want to load in the gallery are of the same dimensions, that way the gallery will look more professional.
To edit the banner images you will need to edit the module itself. To do this simply login to the administration area of your Joomla website and select "Extensions // Module Manager". The banner is located in the position "Promo" so simply select that position and the module will be available to edit.
The video below shows how this is done and also shows how to "unlock" items that you are unable to edit.
Alternatively, watch our short video on YouTube: Changing the Default Banner Images on a JSN Template.