Can be achieved by placing different Bar style furniture pieces, it doesn't matter what type (can be kitchen, chairs, art) as long as it has the Bar indicator in the game.
More Bar furniture will unlock while researching different things at the decoration shrine and you will also be able to unlock some Bar Furniture via friendship levels.
The game will state if you already have 1 of an item and that the stats won't go up, i.e.; have 2 of the same Bar furniture of Bar: 2 stat, is not 4 stat, it's 2 stat.