A - Manually Selecting a Range

First, select the option button next to "Select a range of cells manually" and then click the button to right of the field in the same line.

Select Input Cells

A new window called "Input Cells" will appear. Now you can select the cells that you'd like to convert into inputs. The cell selection works identical to cell selection in standalone Excel.
    - Select a range with the mouse

Select a range with the mouse


    - Select individual cells that are spread the spreadsheet with 'CTRL + Click'.

Select individual cells using ctrl+click

 

    - Type the cell addresses into the form field in the dialog window.

Click "Next" to get to the next step.