@D-D2894 I would suggest contacting your local city hall or Chamber of Commerce to see who to talk to regarding STR requirements. Some places have a waiting list for permits, some take applications for a license, there may be a fee to pay as well. On the flip side, if you've been hosting but not paying taxes on the income to the appropriate department, there can be fines (may be a percentage or a flat fee) to pay until you've complete requirements.
Your letter will likely have a place or person to contact for more details 🙂