GrandPad Prism doesn't have a function that can do this automatically. However, this can be accomplished easily by dividing the text into two pieces. To do this, go to your graph window. Here, press the Add text button (which has the icon a T). In the first box, type
"Black or African" and use the mouse cursor to position the text on the top line of the graph. You should repeat the process for
"American Arg/Arg", but place the text on the next line. This is a simple process that can be accomplished easily.