An account hosting is allowed to host muliple domains in the same account and it is applicable for Basic Hosting and Premium Hosting for shared server. Here are the guidelines to add domains in Plesk control panel.

The Plesk URL may be different according to server and you can use domain name or server hostname link as example (https://domainname.com:8443 or https://hostname.net:8443)

Notes: The addon or new domain should be an active registered domain.

1. Login to Plesk control panel 
   
   
2. On left side panel, select Websites & Domains
   
   
3. On the page, click on Add Domain 
   
   
4. Fill in the addon domain details
   - Registered domain name: The domain wish to add
   - Webspace: Default select the main domain
   - Hosting type: Web Hosting
   - Hosting Settings: will follow the addon domain name 
   
   
5. Let Activate the DNS and Email service enabled
   
   
6. Then, click Add Domain to create the dmain
   
   
7. Once complete, the domain will display on Websites & Domains
   
   
8. Then, you may start manage domain features