The promotion can be found in the Xperia Lounge app, but it is only live for certain phones. For example, whilst it has appeared for the Xperia Z and Xperia Z2 Tablet, it is nowhere to be found for the Xperia Z1, Z1 Compact and Tablet Z in our testing. If you have found the promotion in Xperia Lounge for your phone let us know what model you have in the comments below.
Update: Judging by the comments, it seems that this promotion depends on which region you are in. An Xperia Z1 owner in one country may see the update, but not in another.
Thanks Armaan and Ben!