In Power Pivot, you can add new data to a table by creating a calculated column. The new column can then be used in PivotTables, PivotCharts, and reports just like any other column. Calculated columns require you enter a DAX formula. For example, you could create a new Total Pay column in a Payroll table by entering the formula =[Earnings] + [Bonus]. This adds values from the Earnings column in the same table to values from the Bonus column in the same table for each row. To learn more, see Calculated Columns in Power Pivot.
In the table you want to add the new column to, scroll to and click the right-most column.
In the formula bar, type a valid DAX formula, and then press Enter.
Right click on the column header>Rename, and then type a name.
Note: Unlike Calculated fields, you cannot type a name into the formula itself.