Hi, keep in mind that widgets don’t replicate, they only exist locally so you will need to replicate this in some actor that does replicate and exist on all clients.
To learn more about replication you can download the content examples project and look through the replication examples, doc here Networking Content Examples | Unreal Engine Documentation
This might be too far for beginning, but will be useful to look up things http://cedric-neukirchen.net/Downloads/Compendium/UE4_Network_Compendium_by_Cedric_eXi_Neukirchen.pdf