by SaltyHorse
Yes, the numerals designate which side of the board they belong to. There are four tiles for each numeral, and you can choose which one to use.I goes on the right side, II on the bottom, III on the left, IV at the top.
I may be wrong in some of the details, but this is my understanding:
You place a new guard meeple at the top gate. During your turn, you can perform a new action: "walk the meeple on the ramparts and placing cubes on the outside activities". You spend a single die of any color, and can boost its value with deniers up to a value of 6. Then you can use that value either to walk your guard meeple clockwise on the ramparts/towers (gates are considered 1 rampart - see image in rules), or place cubes on any outside activity whose gate you have passed. You can mix and match the points - for example, if you get a value of 6, you can walk 3 ramparts, and place 2 cubes on an activity II that you just passed, and 1 on activity I that you passed earlier.
During other actions, depending on the activity, you can take cubes off of the activity to activate, similar to how delayed-action cards work.
Once you go back to point 0 with your meeple (activating the fourth activity), you can't advance it any longer, meaning you can only place cubes on any of the four activities.
There's a nitpicky rule related to the "II" activities that give you extra dice - you can't spend a same-colored die to put a cube on them.
I got all this from copy-pasting the French rules into Google Translate - it's sort of understandable :)