Your image looks like it is the trigger action for a selected file. If so, you need to enter/select the SharePoint site and then choose the document library from the drop-down menu.
The workflow can only be applied to one document library. If you need it to run on multiple document libraries, you need to create a workflow for each one and point each to the correct document library.
You don't show your flow, so I don't know exactly what you are trying to do, but if you need the folder path, follow the trigger with a Get file properties action with the ID from the trigger. The folder path is included the dynamic content returned from the action along with a lot of other information about the file:
