How detect an event from a external hardware

Hello:
I return to the forum with the continuation of the problem I had but now I am going more advanced.
I bought a new IoBoard to a new vendor that has an API (NuxIOAPI.DLL) and now I can already enter it in the application and send some controls to it (type releto, activate a port, etc).

Now the problem I have is the reverse: how to receive an IoBoard event.
The command that is required and that is in the documentation is as follows:
ValueEnteredEvent (object sender, ValueEnteredEventArgs, and)

Can anyone help me?

Thank you
Alberto Ferraz