I am happily using KM for a couple of years now, and it is helping me daily to perform my tasks.
Now I’d like to get my head around in automating further based on information on screen. Appreciate if you can point out some good learning repos for me.
To click relative to an image, you use the Move or Click Mouse action, configure it to be relative to a found image, and take a screenshot of the desired area of the screen using Command-Control-Shift-4, and paste it into the image well on the action (Note: if you have trouble with this matching, and you have a retina monitor, check that the captured image is 144dpi - if the system erroneously uses 72dpi, you'll need to correct that to 144dpi). The image has to be unique (which includes not being visible in the action if the image is small enough not to be shrunk in the image well) otherwise Keyboard Maestro will not know where to click. The Display option in the action will allow you to see where Keyboard Maestro is matching.
Similarly for OCR, you can use the OCR Screen action.