Add the specified portal represented by the provided portal Uri to the list of portals. This will result in the ArcGIS.Desktop.Core.Events.ArcGISPortalAddedEvent being published. This method should be called from within a QueuedTask or System.Threading.Task unless the caller is within ArcGIS.Desktop.Framework.Contracts.ConfigurationManager.OnApplicationInitializing in which case the main thread should be used.

public ArcGISPortal AddPortal( 
   Uri portalUri
)

Public Function AddPortal( _
   ByVal portalUri As Uri _
) As ArcGISPortal

var portalUri = new Uri("http://myportal.esri.com/portal/", UriKind.Absolute);
ArcGISPortalManager.Current.AddPortal(portalUri);