If you want to put that text inside of a legend you can do:
legend('Some quick information','location','EastOutside')
That is easiest. For more control though, you can put a text box inside the figure window:
MyBox = uicontrol('style','text')
set(MyBox,'String','Here is a lot more information')
and move it around with:
set(MyBox,'Position',[xpos,ypos,xsize,ysize])