Do you want to get the Art Gallery in your Museum on Animal Crossing: New Horizons? Here's how to do it!
First step: install the update and talk to Blathers
Once the 1.2.0 update is installed on your console, go to the Museum to chat with Blathers. The latter will tell you that he wants to upgrade the museum and offer a section with works of art.
Second step: buy Works of Arts from Redd
We will have to wait until the next day for Isabelle, during the Island Daily announcement, to tell you that a strange individual is prowling on the island. This is Redd! Find him on your island to buy him a work of art.
Just bring a single work of art to Blathers for him to trigger the expansion of the Museum.
Third step: wait
The next day, the museum will be undergoing renovation all day. And the next day, it will be enlarged automatically and Isabelle will make an announcement. Your museum now has a large room hosting works of art!
In total, it, therefore, takes four days of game to unlock the expansion of the Museum.