Grieck,
The code below will add a simple marker symbol to the map at the location of pPoint(iPoint). The size and color are determined by the properties of the SimpleMarkerSymbol. For the labeling, you can use the graphics container to add a TextSymbol at a location that is offset from pPoint - something like pPoint.X + 5, pPoint.Y + 5. I'm not sure about use the style file you mentioned, but I hope this helps.
Justin
Dim pRGB As IRgbColor = New RgbColor
pRGB.Red = 84
pRGB.Green = 255
pRGB.Blue = 255
Dim pPointSymbol As ISimpleMarkerSymbol = New SimpleMarkerSymbol
pPointSymbol.Color = pRGB
pPointSymbol.Size = 10
Dim pPointEl As IMarkerElement = New MarkerElement
pPointEl.Symbol = pPointSymbol
Dim pElement As IElement = pPointEl
pElement.Geometry = pPoint
Dim pGraphicsContainer As IGraphicsContainer
pGraphicsContainer = My.ArcMap.Document.FocusMap
pGraphicsContainer.AddElement(pElement, 0)
pElement.Activate(My.ArcMap.Document.ActiveView.ScreenDisplay)
My.ArcMap.Document.ActiveView.PartialRefresh(esriViewDrawPhase.esriViewGraphics, Nothing, Nothing)