As explained in how to automatically build ships, your 2IC can be asked to plan a complete ship construction program for you for the current turn.
After the program has been prepared, the 2IC Help screen will close and the ships to be constructed will be listed in the ship roster.
If you do not like any aspect of the plan, you can amend it in any way, by removing any ships and replacing them with ones you select or design yourself.
You make these decisions from the Build Ships screen.
This screen will automatically appear when you close the Ship Roster.
To edit the 2IC's plan you need to understand how to select or design ships. Refer to the building ships page for full instructions.