Duplicating existing blogposts is the best way to create a new one, so every layout detail is copied. Go to the tab posts where you have listed all existing posts. Click on 'duplicate this'. Edit the draft that's now created.
Don't forget this:
Set a new title
Assign the correct category (in case you have filters) unless it's already assigned like in this case below
Change the featured image
Change the excerpt text (see photo 2) excerpt text is the text below the main title (if you have this) see photo 3