To do that you’ll need a proper online subsystem implementation. These resources are what you need to do that:
Unreals online subsystem documentation:
As for the actual online subsystem for android you will need to use Google Play Games:
Google documentation:
https://developers.google.com/games/services/android/turnbasedMultiplayer
Google Play subsystem for UE4 plugin
https://github.com/EpicGames/UnrealEngine/tree/e528f9f7fa161504dd629c3b390deac93650e43a/Engine/Plugins/Online/Android/OnlineSubsystemGooglePlay/Source
(Sign up with this guide to get access to it - GitHub - EpicGames/Signup: Information about signing up for a free Epic Games account, and getting access to UnrealEngine source code. )