Hello! I've added those subdomains to your account for you. You may see the folders for them inside Plesk soon, but it may take up to 2 hours for them to work completely. This is because an Apache restart is needed to finalize domain changes, and the restart begins every 2 hours or so.
If after a full 2 hours the new subdomains don't work on your side, please make sure you clear your web browser cache: https://wiki.helionet.org/Clear_Your_Cache