Simply go to Messenger.com and sign in to use the app on your desktop. Alternatively, an unofficial option would be to download a third-party app called Messenger for Desktop. Keep in mind that this is not an official Facebook app, but it will get the job done.
Can I open Messenger without Facebook on PC?
Desktop and laptops users can access their Facebook messages without the rest of Facebook at Messenger.com, and Mac users can opt for a standalone app.
What do people see on Messenger when you delete your account?
When you delete your account, people wont be able to see it on Facebook. Some of the things you do on Facebook arent stored in your account. For example, a friend may still have messages from you even after you delete your account. That information remains after you delete your account.