To better engage use the tops of your toes rather than the bottoms to balance on.
Once you’re ready to descend, keep your butt and belly squeezed while lowering, don’t let the middle sag whatsoever. As the elbows bend they need to stack over the wrists. At the very bottom the thumbs should be turned out, elbows stacked over wrists and an active core before driving back to the top. Use your knees to reset to a solid plank position before starting from the top again.
Keep tight throughout the movement and don’t let the shoulders or middle sag.