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This sample code shows how to add an edit operation to your code when using the IEditor interface.

Code:
Sub addPointToFirstLayer()
  Dim pMap As IMap
  Dim pMxDoc As IMxDocument
  Dim pFeatLyr As IGeoFeatureLayer
  Dim pFClass As IFeatureClass
  Dim pDS As IDataset
  Dim pWor As IWorkspace
  Dim pEditor As IEditor
  Dim pID As New UID
  Dim pfeat As IFeature
  Dim pPoint As IPoint
  
  pID = "esriCore.Editor"
  Set pEditor = Application.FindExtensionByCLSID(pID)
  Set pMxDoc = ThisDocument
  Set pMap = pMxDoc.FocusMap
  
  Set pFeatLyr = pMap.Layer(0)
  Set pFClass = pFeatLyr.FeatureClass
  Set pDS = pFClass
  Set pWor = pDS.Workspace
  
  pEditor.StartEditing pWor
  pEditor.StartOperation
    Set pfeat = pFClass.CreateFeature
    Set pPoint = New Point
    pPoint.X = 2212000
    pPoint.Y = 397000
    Set pfeat.Shape = pPoint
    pfeat.Store
  pEditor.StopOperation "Add Point Feature"
  pEditor.StopEditing True
End Sub

Code:
Sub addPointToFeatureClass()
  'Assume we have a reference to IWorkspace called pWor and a feature class called pFClass
  Dim pfeat As IFeature
  Dim pPoint As IPoint
  
  Set pEditWS = pWor
  pEditWS.StartEditing True
  pEditWS.StartEditOperation
    Set pfeat = pFClass.CreateFeature
    Set pPoint = New Point
    pPoint.X = -59.05
    pPoint.Y = 51.11
    Set pfeat.Shape = pPoint
    pfeat.Store
  pEditWS.StopEditOperation
  pEditWS.StopEditing True
End Sub