From the Recap: You can now signup for the NWN: EE beta on Steam:

February 9 Livestream Recap

Today’s livestream with Beamdog CEO Trent Oster and Studio Director Phillip Daigle revealed two big updates for Neverwinter Nights: Enhanced Edition - new character models and news about the NWN:EE beta on Steam! They also shared news about the open beta for the upcoming 2.5 patch for Baldur’s Gate: Enhanced Edition, Baldur’s Gate II: Enhanced Edition and Icewind Dale: Enhanced Edition.

Missed the stream? It's on YouTube and Twitch!

[...]

• Throughout the coming week, we will be rolling out early invitations to the NWN:EE beta on Steam. If you hop over to our special Discord channel you will be able to request a Steam key. Invitations will be limited on a day-to-day basis. On Feb 16, we plan to email all Neverwinter Nights: Enhanced Edition Head Start owners beta keys.
• Activating a Steam key doesn’t disable your Beamdog version. When the beta is over, beta Steam keys will deactivate and Head Start owners will be supplied full NWN:EE steam keys for all NWN:EE content purchased.
• The NWN:EE beta on Steam will support the Steam Friends List. It’s as easy to use as you could think: on your Steam overlay you choose the Friends List and invite a buddy into your game, without any port-forwarding on your router.

[...]

Thanks Farflame!