A profit and loss statement does not include opening and closing stock levels. It includes only income and expenses. You can generate one under Reports.
If you want Manager to track stock (inventory) levels, you must enable the various inventory-related modules. Read about that in the Guides.
Your questions suggest you are not familiar with double-entry accounting. So you should spend some time learning about it. You might start here: http://www.accountingcoach.com.