Basic Macro Question

Sorry in advance, this should be a simple fix I just have zero experience with Macros in excel. I have this set up so far. The number of rows varies so I find the last row. I then want to plot data from columns A&B from A4 to LastRow and B4 to LastRow but am not sure how to do this. Thanks in advance

Sub PumpingCurve()
'
' PumpingCurve Macro
'
    Dim LastRow As Long
    With ActiveSheet
        LastRow = .Cells(.Rows.Count, "A").End(xlUp).Row
    End With
        ActiveSheet.Shapes.AddChart.Select
    ActiveChart.ChartType = xlXYScatter
    ActiveChart.SeriesCollection.NewSeries
    ActiveChart.SeriesCollection(1).Name = "=test2!$A$1"
    ActiveChart.SeriesCollection(1).XValues = "=test2!$A$4:$A$"
    ActiveChart.SeriesCollection(1).Values = "=test2!$B$4:$B$"
    
End Sub