How do I submit a T2L(F) document via NID?

Similar to the way you did this prior to the Proof of Union Status (PoUS) arrangement.

However, the role you fulfill determines which option applies to your organization:

• Shipbroker
  You create an NID notification for the document type ‘ICT’ and supplement this notification with the MRN number of the document.
• Cargo interested party
  You create a NID notification for the document type ‘FWV’ and supplement this notification with the MRN number of the document.

Customs explained the entire procedure in question 12 in a Q&A following a meeting that Portbase had organized. You can read the full Q&A here.

Cargo Declaration Import 2.0

It is important that the MRN number you use is also specified as such by the shipbroker in the import manifest. You can read more about those actions here.