I've added that domain to your account for you. It's not possible to add wildcards, but you can have have up to 10 domains in total (including addon domains, subdomains, and aliases (parked domains)), for free on your account, so please let us know if you want any more added. 😺
Please note that it may take up to 2 hours for the new domain to fully work. If after a full 2 hours it doesn't work on your side, please make sure you clear your web browser cache: https://wiki.helionet.org/misc/clear-your-cache
In the meantime for the domain to work, please either:
Point your domain to the HelioHost nameservers: `ns1.heliohost.org` and `ns2.heliohost.org`, or
Create A or AAAA records and point them to the IP addresses for the server you're on. You can find the IP address to use inside Plesk > Websites & Domains > [domain name] > and check at the bottom of the page.