The problem with these lines is that you are trying to set one cell (the
active cell) equal to 3 cells (D13:D15).

ActiveCell.Value =
Workbooks("ReportRP.xls").Sheets("PS").Range("D13: D15")
ActiveCell.Offset(0, -1) = _
Workbooks("ReportRP.xls").Sheets("PS").Range("I6:I 10")

If you wanted to put the 3 cells at the bottom of the list, then you could
use

ActiveCell.RANGE("A1:A3").Value =
Workbooks("ReportRP.xls").Sheets("PS").Range("D13: D15").VALUE

This would place the cells D13:D15 into the active cell and the 2 cells
below it (the A1:A3 bit is relative to the activeCell)