starting the downswing with the hips?

ive been struggling with just an arms swing recently, not using the rest of my body enough. i watched a you tube video and it mentioned that you should start the down swing with your hips? is this correct?

Liam, The pros do this. The belt buckle rotates toward the target just before the downswing starts. This adds extra power. I as you do, use only my upper body but am trying to incorporate this Hip turn into my swing. There is a few good vids on UTUBE. Dave CAC handed Geordie.

From 30yds into the green I seem to be starting my downswing with the yips.