Localizating strings on script

Hi,
I’m developing a game with multi-language support.
I’m able to correctly do the localization of buttons and text label in the UI, but now, I’ll new to localizate some text via script as they are error messages shown on a unique text label.

How to do it? How do I get the localizated value (text) of a known localizated key in c#?

I tried with that code:

                    LocalizedString localized = new LocalizedString();
                    localized.TableReference = "Texts";
                    localized.TableEntryReference = "USERNAME-ALREADY-EXISTS";
                    Debug.Log(localized.ToString());
                    Debug.Log(localized.GetLocalizedString() );

but do not works I get that:

[TableReference(Texts)]TableEntryReference(USERNAME-ALREADY-EXISTS)
UnityEngine.Debug:Log(Object)

UnityEngine.ResourceManagement.AsyncOperations.AsyncOperationHandle`1[[System.String, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]]
UnityEngine.Debug:Log(Object)

Thanks

Generally we load a CSV or some other way of storing key, language combinations, and you just make a module that can retrieve that from a Dictionary that it gets loaded into.