This image won’t upload because it’s more than 1MB.
Trouble is, if I resize it, the overlay effect will go.
Help please?
The image you have posted here is a jpeg, so the screens are going to have the white in them (not be transparent). Overlays should be formatted as a png file.
That’s why… So how do I make it overlay?
In her interior folder, shara.stories on Instagram has that background as an overlay with transparent screens. Make sure to credit her if you choose to use it.
Thank you. 
Very weird, I downloaded her image which was in PNG and transparent but when I download into overlay it still says it’s over 1MB.
If you haven’t already, use a site like this to compress the png file.