Steps to Add Derived Field

Following are steps to add derived field

Write variable name which you want to add as a derived field in the Name field.
Select data type from the Data Type combo box.
Click on Add Button.
To add a derivation/formula for reference field select Create Derivation option.
Select the field which will appear in derivation from list and click on Add Field to tree Button.
If you want to remove field added in the list then select the field and press Delete key on keyboard.
Add minimum two fields in the list.
Select the operation to perform on selected fields from Arithmetic Operation combo box.
Select both fields added in list and click on Create Resultant Button.
Select Derived field and resultant formula and click on Assign Result to Derived field Button.
Click on Ok Button.