Your out of my safe zone but here are the steps I would take if you are still in a vacuum.
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enable Game Center in your project settings
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go to developer.apple.com and enable the Game Center for your project (this is all Apple not unreal)
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enable the IOS online subsystem in default engine.ini
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look up how to get two clients in the same session (keywords - matchmaking, find session, host, client, LAN, server)
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look up how to send a reliable message between your clients and how to receive it (TCP/IP, messaging, reliable)
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take a deep breath, the starting setup to multiplayer development is often a bit tricky but once you are working on actual gameplay it gets way more interesting, and difficult!
If there is some turn based code that’s cool for you as keeping clients in sync through gameplay progress is not entirely trivial but at the end of the day it’s not that complicated either (lots of borderline what happens if client a drops while situation b is happening stumbling blocks) so if you’ve got some nice in order reliable messaging system you are away!
My guess would be some good samples are lying around for all this.
Good luck 