Included with your Showcase Pro theme purchase is the following PSD file of the iPhone screenshot displayed on the Showcase Home page.
Next, upload your iPhone picture to your Media folder on your Dashboard. Grab the image URL it generates after the upload is complete.
Go to Appearance > Widgets. In the Front Page 2 widget area, place a Text widget with the img code, like so:
Swap out the link between the quotes for your iPhone image URL. Also, notice the class “pull-right”. This class is there to give the effect of the iPhone screen overlapping the edge of the screen on certain screen sizes.