Make sure you send the instance_id and the submission_id into fields in Laserfiche. I like to have that information available, just in case you need it for the future (never hurts).

Then in Workflow, add a "Retrieve Laserfiche Forms Content" activity to your workflow. To start configuring the activity, click the little gear in the upper right corner of the properties pane. In "Retrieve the content from:" field, either choose the instance that started the workflow or choose "The instance with ID:" and enter the field that has the instance id in it. Do the same with the submission id.

Click the gear again to configure the rest of the properties: enter the Forms server, the process that sent the form to Laserfiche, and then click under the Forms process and select the fields you're interested in (be sure to select the table you're interested in). To do something with each row  in that table, you'll need to process it with a "For Each Row" activity that follows the "Retrieve Laserfiche Forms Content" activity. The rest should be simple Workflow stuff.

I hope this helps!