Create your intro and conclusion either before you start on the main body of the article or after you create the main body. Practice writing out intros and conclusions before writing the main body of the article for the next 3-4 articles you write. After that, create your intros and conclusions after you write the main body of your articles. I suggest doing this because then you'll be able to judge which is easier and quicker to do.

Personally, I bounce back and forth between the two. As for how to create your intros, that's easy; Simply refer back to your blueprint and it should flow from there.

I know the above is commonsense info, but trust me that practicing creating intros/conclusions repeatedly will help you write faster.