Click on Artwork in the left-side menu, then select Runs/Reproductions underneath. Under Runs and Reproductions, click on + New Run.

Select the Piece for which you'd like to create a run by typing its name in the search bar in the Pick Your Piece box. Fill in the Run info and click on the blue Create Run button.

Or, you can also create a run by selecting the original Piece. 

Click on Artwork in the left-side menu, then select Pieces. Click on the Piece. Then, click New Run in blue next to Runs/Reproductions in the right-hand column. Fill in the information and click Create Run.