How to add downloads back to dock?

I removed Downloads from the dock so it only shows in finder. How do I add Downloads back to the dock?

Also, my Downloads folder somehow got out of order. It used to be in order so that whatver I downloaded showed at the top of the folder. Although I tried sorted it by date, I guess the soring feature is not working since nothing happened. When Downloads did show onthe dock, I still could not open the downloaded file by clicking on its icon in Downloads on the dock. I don't know if you can open the downloaded file icon fronthe dock. The problem is I am unable to read what I download because I can't find it (due to be ing downloaded out of order) or open it. I wonder if the you can delete what is in the Downloads folder as well since I didn't see a way to delete it so I could clear everything to see what downloads when it downloads.