How to show given x,y position on image frame?

I am trying to show shape connecting 3 x,y points on image frame.

fileCount=length(Files);
middleImage=round((fileCount/2)-5);
startingImage=Files(5).name;
middleImagePOS=Files(middleImage).name;

imagename1 = fullfile(outputFolder, middleImagePOS);
originalImage = imread(imagename1);
 out = insertShape(originalImage,'Line',[
     ex_points{5}(1,1) ex_points{5}(1,2) 
     ex_points{5}(2,1) ex_points{5}(2,2) 
     ex_points{5}(2,1) ex_points{5}(2,2) 
     ex_points{5}(3,1) ex_points{5}(3,2) 
     ex_points{5}(3,1) ex_points{5}(3,2) 
     ex_points{5}(1,1) ex_points{5}(1,2)
     ] );
%grayImage = insertMarker(originalImage,pos,'+','Color',color,'size',20);
imshow(out);
% plot([shoulder_X elbow_x wrist_x], [shoulder_Y elbow_y wrist_y],'g');
F = getframe;
imshow(F.cdata);

ex_points{5} -> is array which include x,y value of point a,b and c.

How can i show this shape on the image which i take? if that insertShape() worked, it should show the image like below