I've been battling with this all day, it wouldn't show up in the simulator or a real device.
Eventually I got it to work by making sure the Target Membership for the AppIcon was set to the app name and that the Location was "Relative to Project".
In my case these two options were set wrongly
On 6/19/18 Apple released Xcode 10. beta 2. Upgrading solved the problem I was having with icons not appearing. So, a bug in Xcode 10.0 I guess.
