Click Picture to see a larger image.
To add a background picture to Daz Studio... Click the Environment Tab... Click the first column of the Background field and it will drop down... Browse to your picture.
To have the Background picture appear in your Viewport... click the 2nd icon... on the dropdown click on NVIDIA Iray.
You can also see your render by going to Window...Panes (tab)... Aux Viewport. This will bring up another small viewport that can be resized to see what the render will look like.