Apartment is right in the City Centre. Get the bus into O Connell Street and get out just at the River Liffey.
Then ask for Halfpenny Bridge - its a very famous pedestrian landmark bridge over the River Liffey.
Once you are at Halfpenny Bridge on the north end look for Liffey Street. Apartment is on the right, 50m from the Bridge.
Entrance is right beside Halfpenny Bridge - its the big door beside the Barbers Shop.