In queries you turn on the total row,[right click ,in design view and click on the sigma symbol] that should make it easier for you to figure out.
On reports
Open the report in Design view.Add a calculated text box to one or more of the following sections:How?To calculate a total or average for a group of records, add a text box to the group header or footer.To calculate a grand total or average for all records in the report, add a text box to the report header or footer.To display the property sheet, make sure the text box is selected, and then click Properties on the toolbar.In the ControlSource property box, type an expression that uses the Sum function to calculate a total or the Avg function to calculate an average. Tip In a Microsoft Access database (.mdb), you can click the Build button to use the Expression Builder to create the expression
Hope that helps!