lets suppose you want to add the values in column b to comments in column a
here is the code
Dim i As Long
Dim x As String
For i = 1 To Range("a1").End(xlDown).Row
x = Cells(i, 2).Value
Cells(i, 1).AddComment x
it will add value of b1 as comment in a1, b2 as comment in a2, b3 as comment in a3 and so on.....