On our homepage at www.checkdomain.net/en click on "Login" in the top right corner to log in to your customer area. 

In the left navigation click on the navigation point "Server Manager".

Click on the gear to the right of the desired package and select "Add package domain". 

Now select whether you want to add an already registered domain, an external domain or a domain that has not yet been registered. 

In our example, we add an already registered domain to the web hosting package.
Click on the "Add existing domain" button to do this.

Now select the desired domain and integrate it into the package by clicking on the "Add domain" button.

The following screen appears:

Here you can select whether the domain is to point to the main directory (/htdocs) of the FTP server, whether a separate directory is to be created or whether a forwarding is to be set up.

Attention: A separate directory (individual folder) must be selected if the domain is not to point to the same website as the other domains in the web hosting package.

For external domains there are one-time costs for adding the domain. If this is the case, you will be notified accordingly.

Finally, confirm that you have read the above information by clicking on the corresponding 
Place a check mark in front of the text.

Confirm your entries by clicking on the "Save" button.