Once you are in the town square and have the handle to operate the town clock you will need to read 2 signs on the wall in order to see 2 different times and get people to enter the building.
There is a 3rd note showing a 3rd time on the right hand side of the door and this is the time we need in order to get the Turban man to appear from behind the shutter above. The note has a symbol of the moon followed by 3 times so I used the 1st in the list)
The time we need to enter is the symbol for PI (around the 2pm area) and IX
Once this is done and you back out he should appear above and the achievement will unlock