Go to "File"
then select "Preferences"
under sub menu "General", frame section "Label" tick/untick" the following:
-untick Square Label
-check font and font size
If you have too many airframes in an area, all label -containing the flight number, registration and altitude, rate of descend, speed- will disappear, to keep the radar screen "readable". If you zoom in the map to get a lower airframe per area rate the labels should reappear. As far as I know, there is no option integrated to fully remove the appearance of this data-labels.
Next time please be more specific with your problem. Because the way you state your question was on the edge to require mind-reading capabilities.