Calculated Fields
In the field list, select the section you want to create the calculated field. Right click and select Add calculated Field.
The system will then create a field with the name 'calculatedField1' you can then rename the field by going to the property grid below and changing the field name under name.
Find your new calculation, right click it and select Edit Expression.
This will bring up the expression editor where you can define what the new field is.
Here you can use functions, operators and fields we already have to create the expression.