There are two ways to open the simulator. From your account, by opening My Apps and pressing Open next to the FAP Trainer A320; this is the usual way to test and configure. For the computer installed in your simulator there is kiosk mode, which opens the FAP without asking for a login.
Kiosk mode uses a personal link of the form flightdemy.com/fap/XXXX. You will find it in the configuration panel, Hardware tab, as the Screen controller URL: copy it and open it in the simulator computer browser. It is best to pin it as the start page or a shortcut.
The first-browser rule
For security, the link binds to the first computer that opens it. From that moment only that computer can use it: any other browser opening the link will see a message that the code is already bound. This way, even if someone knows your link, they cannot enter your simulator.
If you need to change the simulator computer, first unbind the current one from the Hardware tab and open the link again on the correct computer. If you suspect someone else saw your link, use Regenerate to create a new code and invalidate the previous one completely.
Fullscreen and startup
With automatic fullscreen enabled, the browser goes fullscreen on the first tap on the screen. No browser can do this without that first user gesture, so an initial tap is always required.
The start overlay shows a Start screen that unlocks audio and fullscreen. If you disable it, the simulator will try to start directly; test it on your computer, because some browsers block audio without a prior gesture.