Problems with hdmi output on Zedboard with PYNQ

I am now using PYNQ v2.4 to run it on my Zedboard Zynq 7000. I can now run code to capture a photo through the webcam but it is not able to output to the screen through HDMI to implement the real time face detection running as video. I have tried to follow some tutorials but I am actually still a beginner, not quite able to understand or complete the overlay myself even though I tried to follow the tutorials. Could anyone help me on this or give me some hints? Thank you

You need to provide more information about your problem.
What have you tried?
Do you have an overlay design that includes a HDMI controller for the Zedboard?