Cartes du Ciel is free software released under the terms of the
GNU General Public License
You can configure the automatic display of labels in SkyChart by Setup → Display → Labels.
You also can set the font type, the font size, color, and which kind of objects to label.
For stars and constellations you can set the type of content to fill the labels.
You have to set the „Edit label” mode to „on” with the icon. Also, make sure that the display of labels on the chart is enabled by checking that the icon is pressed. Then, if you right-click on a label, a pop-up window will be diplayed with these entries:
To add a label, first you need to provoke a pop-up window by a right-click on an object or anywhere on the chart. (If you want more information about the pop-up window, see Pop-up windows.)