Fairytale of New York is an achievement only available on the New York (Christmas) map
I recommend you have the "show heist tips setting on
This achievement can be obtained with 1 or more players on each team but u need to be on the robbers team
All you need to do to get this achievement is find three Christmas themed secrets around the map
u can check ur progress by looking at ur steam achievements

The first secret is the newly added green presents around the inside of the bank, they have multiple spawn points and picking up even one of them will get u the first part of the achievement.

For this part all u need to do is put any bag in a chimney, this chimney is located on the roof of the building closest to the entrance of the bank, the chimney can also be found by picking up a bag and viewing the icon which looks like this:


The chimney looks like this:

This is the hardest part to do, in order to get this achievement u need to shoot a teleporting Santa (usually) once

Santa will be teleporting between the two buildings shown below every around 15 seconds







Simply shoot Santa and u should get this part of the achievement

After doing these three steps u should have the achievement!
thx for reading the guide, hope it helped! :3