At Hostinger, you can host several websites in your cPanel hosting plan by following these steps:

First, make sure you have ownership over the domain. If needed, you can purchase it.

After completing the domain registration, open the domain management page on your current domain provider, and set Hostinger’s cPanel nameservers using the following values:

When applying these changes on your domain's DNS records, consider they will require up to 24 hours propagate. During that time, the domain may be briefly unavailable. Give it some time, and it will start working soon – usually, a couple of hours is enough.

To ensure everything works properly, proceed to the next step only after propagation is completed.

If you're using the Jupiter theme, access your cPanel account and click on the Domains section:

Next, click on Create a new domain:

Enter the following information:

Once it's good to go, click on Submit:

You will also be able to remove and manage your addon domains at the bottom of the page:

That's it! Now you can start developing your website from scratch, or upload an existing website from backups.