Productions are collections of drills combined into one file to make a production. When you select Open Production you will see the list of drills within the production to open.
Select Open Production from the File menu.
You will see in the Open dialog the list of productions. Click on a production you want to open and click Open.
The list of drills found in the production will display. Click on the drill within the production you want to open and click Open.
When a production is opened you can only work with drills in that production. To work with other drills not in the production you will need to first close the production by using Close Production from the File menu.