Add will display a window enabling you to enter text. After clicking the Add Text button, the text will appear next to the airport selected in the chart. The text can be moved by clicking and dragging the text. It can also be rotated by moving the mouse to one of the corners of the text until the cursor changes to rotating circles and the click and hold the left mouse button and move the mouse up/down or left and right.
Delete will delete selected text on the chart. To select text click on it and it will show a yellow box around it. Selected text can also be deleted by simply pressing the Delete key.