If you already have the requirements, all you need to do is to fly to Ha Long. When you arrive at the airport, look for the visa counter and submit the requirements. The officer will review your requirements and will ask you to be seated. After a few minutes, the officer will call your name. Your passport will be given back to you and it will already have the visa sticker in it. Double-check the information on your visa and make sure everything is correct. If there are any problems, inform the Immigration officer immediately.
After getting your passport back, you can proceed to Passport Control. Give the officer your passport and it will then be stamped so you can enter Vietnam and start your holiday in Ha Long Bay.
https://www.vietnamimmigration.org/what-is-the-procedure-at-vietnam-airport-to-get-the-visa/
