Create a new workflow element called "Get File List". It should take the following parameters:
- "Input directory" with the "..." button
- "File path" with values "Absolute" / "Relative"
- "Read" with values "Recursively" / "Only this item"
- etc. (see the "find" Linux utility for more ideas)
The element should have output slot of type "String". It should pass to the output a read file path (one by one).