Creating a new banner is the first thing which you need to do .In order to do this
Next you need to publish a new module to display your newly embedded banner. In order to do this
In order to create a Joomla Banner Client click on Components >> Banners >> Client and then click on New button on the toolbar. Then fill in the required details. All the fields must be filled else Joomla will not allow you to save your records. Make sure that the client name that you enter reflects the banner that you are going to create, because you might have a number of banners after a while and you will always want to associate the correct Banner Client to each ad that you display.