Assuming you already enrolled in a developer license program and have an apple id.
Follow these steps:
open up file name with extension .xcworkspace
Navigate through Project Name > Targets > General
1. Change the display name of the app, this is what the name of the app that you want the users to see in their devices.
2. Provide an unique bundle identifier of the
First, you should have a great design for your icon and file should be in PNG format with size 1024 x 1024 pixels.
Second, use a free online tool like https://makeappicon.com/ or http://appiconmaker.co/ to size down your icon for all different sizes for the Apple App Store or Google Play.
Finally, upload them when you submit the app.