Breathe or huff the air over the call. Bring the air out of your diaphragm. Your tongue placement is not as critical as air flow right now. Getting noise and remembering how you got it is. Once you figure out how you made the noise then you can begin to move the tongue and apply different pressures to make it sound different. Try to open and close your mouth with every note or sound. I say oup or elp for the yelp. Keeping it in your mouth and practicing will get you there.