There are some settings you can change directly in the Client by clicking on Options. Don't forget to click on Save changes if you change something.
General Client Settings
automatic login at startup
The Client saves your username and password and logs in automatically at startup.
use simple fueling method
On the refuel page you just enter how much fuel you want instead of having to set up each fuel tank.
Sounds (buttons and end flight sound) are activated.
Flight Simulator interface
Choose which interface is used to communicate with the Flight Simulator: Automatic (the Client tries one after another), FSUIPC or SimConnect.
In Flight Settings
flight monitor tracking
If activated, the Client sends regular position updates to the website (to update the Flight Monitor) during your flight. This function sometimes causes trouble if there is a bad internet connection, so try turning it off if you experience problems with the Client (e.g. blank screen).
display text in Flight Simulator
Show text messages about flight state, failures and penalties inside your Flight Simulator. This doesn't affect the 'abort' message which is always shown if you try to cheat on a flight.