Step 1: Add an 'Input Splitter' to your QC patch and set its to type 'Image'.
The video stream from VDMX will be passed in from here. Connect this to parts of the patch that process the image as needed.
Step 2: Publish the input for the image using the key 'inputImage'
Add and publish Input Splitters for any variables to control from within VDMX.