I just started using OS 10.15.7 (Catalina) on a new (to me) MacBook Pro. I save lots of images and screengrabs from my desktop. I see Grab has been replaced by something called Screenshot. I find it as difficult and incomprehensible to use as I found Grab easy & straightforward. I can't do anything with it. It won't even let me put it on the dock. Can someone tell me what I'm doing wrong?