A slide consists of three layers - the bottom layer is the background, which are the designs and colors that make up the appearance. The next layer is the layout layer, which is over the background and it determines the position and type of contents.
Top layer is the slide layer.
Make sure Presentations Slide Show is highlighted and click Create Explain that presentations has different categories for the backgrounds. Access the various categories by clicking the drop down arrow. To the right of the tabs is the New Slides icon. This will let you create a new slide. Then there is the new slide list.