When you buy a train through this site, you will receive by email a link to an .exe installer, along with a key code. The key code is unique to you and traceable back to you. (It may happen that the said e-mail ends up in your spam folder. Therefore, check that folder if you do nothing to have received).
You may need to temporarily disable any antivirus software to download the installation file.
You can save the file where you want to, but please keep a copy of this file on hand (backup) in case you need it again. This is also true for the key code.
After starting the installation (double-click the installation file), you will be asked for the location of the game (TS2015).
This is usually c:\program files(x86)\Steam\steam apps\common\rail works.
The installer automatically uses the location of the game as it can detect this.
The program will then put all the files in the appropriate folders of the game. You do not need to install anything manually.
Once installation is complete, you must train(s) can see in the Quick Drive menu.