Make an image appear on screen

Hi, I'm really new to this and what I want is for an image from a .png file to appear on screen at a location of my choice. This is what I have so far:

Code for fixation cross:

screenNum=0;
[window, rect] = Screen('OpenWindow', screenNum, 1);
[X,Y] = RectCenter(rect);
FixCross = [X-1,Y-40,X+1,Y+40;X-40,Y-1,X+40,Y+1]; 
Screen('FillRect', window, [255,255,255], FixCross');
Screen('Flip', window);
HideCursor;
WaitSecs(2);

name associated with the image:

green_down = 'GreenDown.png'; green_downarrow = imread(green_down);

I want the image(green_down) to appear in a particular quadrant on the same screen as the fixation cross. I tried using imshow, but that causes a new window to open and that isn't what I want. Also, I am using psychtoolbox, if that means anything.

Any help would be greatly appreciated, thanks,

Brett