To add a new slideshow image or rearrange images, in the Admin go to Content > Slide shows. Choose the slideshow you wish to change (usually it will be HOME).
To add a new slideshow image, scroll down to an empty slide and select "choose file" next to "image". It will offer you a browser for your computer, so just select the file and hit okay. Then just scroll to the top or bottom of the slideshow page and hit "save", and you're done!
If you want you also can add a destination URL for that banner image. That means that when someone clicks on the slideshow image you've put up it will take them somewhere. For example if you have a Tacori banner, you can have it be clickable and go to the Tacori brand page. In order to add a destination URL just put the desired destination URL into that "URL" field.
You can control the order of the slides by changing the numbers around in the "Order" field. You can make certain slides inactive if you don't want them to show, or you can completely delete slides if you'll never want to use them again.