Hi Ricardo,

After a form is submitted, you can use either Forms or Workflow to capture the form's instance ID. 

To configure this in Forms, in the Process Modeler use the Save to Repository service task. Within this service task, you have access to a list of tokens related to the form, including Instance ID. I recommend that you create an Instance ID metadata field to hold this value, which Workflow can then access and utilize. This answers post gives the details on configuring the field, and this one offers more ideas on how to utilize it. 

If you'd rather not save the form to the repository, then in the Forms Process Modeler use the Laserfiche Workflow service task. Under Workflow Name, specify the workflow to be kicked off. To configure that workflow to capture the form's instance ID, first right click on the workflow's canvas and select View Properties. Under General, check the Attributes option that says "Started by Laserfiche Forms." Now you can access a list of tokens related to Forms, which includes the token BP Instance ID. This list is under the heading Input Parameters (as opposed to Global). The image below shows the Input Parameters list and the BP Instance ID token, which I accessed via the Assign Token Values activity.