How to make a background for a png image that could be used for layout?

Question

PSD

There is a red background and a png picture of an iPhone, but you need to make it so that the iPhone screen has a white background and make a textarea, what to do with the picture so that you can immediately take the iPhone picture with a white background during layout?

Answer 1

A bit late, but still.
I would do like this:

After that, export everything to PNG (Menu - File - Save for Web, choose the format, transparency, etc., or just "Save As" - and then choose PNG).

Rejoice in the image of a smartphone with a white screen.