Public Overridable Sub PreviewFullScreen( _
   ByVal _bsChannelID As String, _
   ByVal _bFullScreen As Integer, _
   ByVal _nDisplay As Integer _
) 

public virtual void PreviewFullScreen( 
   string _bsChannelID,
   int _bFullScreen,
   int _nDisplay
)

public procedure PreviewFullScreen( 
    _bsChannelID: String;
    _bFullScreen: Integer;
    _nDisplay: Integer
); virtual; 

public: virtual void PreviewFullScreen( 
   BSTR* _bsChannelID,
   int _bFullScreen,
   int _nDisplay
) 

Parameters

_bsChannelID

channel ID. By default use empty string

_bFullScreen

0 is to disable full screen, 1 is to enable full screen mode

_nDisplay

index of a display where full screen will be implemented

Here is example of how set preview into full screen mode on a second display:

m_objPreview = new MFPreviewClass();
//Configure preview
m_objPreview.PreviewWindowSet("", panelPreview.Handle.ToInt32());
m_objPreview.PreviewEnable("", 1, 1);
m_objPreview.PreviewFullScreen("", 1, 1); // enumeration of displays starts from 0

Reference

MFPreviewClass Class
MFPreviewClass Members