There are 3 Signal Boxes on the railway, and a simulator has been made for each one. Why not have a go and see how you get on?
Simply download the required simulator to your computer and extract the files. Once extracted, open the folder and click on the setup icon, then follow the instructions. Once installed , you should be able to access the simulator via your start menu. The help and readme files are located in the main folder for the simulator, normally in Program Files on your main C:/ Drive.