You can add calculated values into Text elements or Table cells by writing a data field name or an expression inside square brackets.
The client's name is [ClientName].
The total amount is [SUM(Amount)].
These aggregates will be computed across the current set of grouped rows. Therefore, they are usually used in Text elements in group header or footer sections, report header or footer sections, or table footer rows.
There are [Quantity] items at [UnitPrice] each, for a total of [=Quantity * UnitPrice].
See Functions for the list of available aggregate functions.
The subtotal is [=FORMAT(Quantity * UnitPrice, '$#,##0.00')].
More information about FORMAT and other functions is available at Functions.
Single data field names and aggregate functions can be written without a leading equals sign. All other expressions must begin with an equals sign.