Workflow offers a couple of options when working with Sharepoint.
There is the Integration Component for Sharepoint List manipulation or there is the library.
New Integration Component Choose "Microsoft" SharePoint Lists Generator
Next fill in your details
Choose which Lists you want to work with
Give it a Namespace and Component names
Add this Library to your Workflow and pull in the components you need.
You can use the Search Items where ID - IS NOT NULL if you want all items returned.
Precreated DLL
Another option is to use the DLL created by Symantec. Create a Web Forms project and add in:
LogicBase.Components.SharePoint.dll
This will then prompt and tell you new Properties have been created.
When you drag on a component some Properties will be created for.
Go to the Project Root then the Properties Tab.
There will then be a number of Components available to you:
Forum
https://www.symantec.com/connect/forums/workflow-reading-sharepoint-list
https://www.symantec.com/connect/forums/workflow-and-sharepoint-lists
https://www.symantec.com/connect/forums/how-get-list-items-sharepoint-list-within-workflow
Articles
https://www.symantec.com/connect/articles/symantec-workflow-and-microsoft-sharepoint