Please download WinSCP from https://winscp.net/eng/download.php and use at least Version 5.8, because file locking won't be functional otherwise.
Start the Software with a double click and follow the installation wizard.
Start of WinSCP
After starting WinSCP, the following window opens:
Choosing the Settings
Use WebDAV as File Protocol and choose web-upload.rwth-aachen.de as host name. Set TLS/SSL as encryption and type in username and password:
Go to Advanced and type in the path to your webspace as remote directory (also retrievable via Webhosting Portal):
Accept the settings with OK and start the session with Login.