There are therefore two options:
Each point where a movement is allowed to proceed is a regulating decision and you can let the booking boy make all these decision, the best he can. Alternatively you can elect to make all the decisions and just let him do the work. However you cannot change your mind again. To make the decisions yourself, click on the inset box where it says 'Click: go to manual'.
In manual mode, where you make the regulating decisions, movements may be allowed to proceed by clicking over the red text (you can also click over the red text in 'auto' mode to make individual decisions but this is not without risk). There are a number of conflicting movements which need to be regulated. The fundamental purpose of the signalman is to regulate the trains safely and to minimise delay. Not all delay can be avoided as some compromises are made in the timetable (especially on summer Saturdays!). The score, which is continuously displayed, contains penalties for late running and for operation outside the regulations, with penalties differing according to the severity of the error.
In the free version, you can therefore choose to watch a demonstration of the whole sequence of trains proceed, with someone else pulling all the levers and operating the block bells. You see and hear the result, with a commentary scrolling up explaining what is happening. The score stays at 100% as no mistakes occur! To operate the simulation yourself, just click on the 'Simulation Speed' box within the first 20 seconds and you are on your own!
In the full version, the deminstration mode is more complex, with many movments operating in parallel - again you can just watch a demonstration or you can operate as a superviser, just making the regulating decisions, leaving the details of pulling the right levers and sending the right bell codes to a menial. A taste of how this works is provided for the last two movements in the free version where you choose in which sequence they depart.