In your welcome email, you most likely saw a section like:

 "To ensure your web hosting works correctly, you will need
to delegate* your domain to the following nameservers:

If you registered your domain at Webcity, you can safely ignore this message.

If your domain was registered elsewhere, this means that your application for a professional hosting plan is not yet complete. You will need to get in contact with the people who registered your domain name and ask them to change your nameservers. Sometimes this will require a phone call, sometimes it will require an email, and we cannot be responsible for doing this part of the process for you.

Once you have been in contact with your registrar, you will need to ask them to change your NAMESERVERS to the following:

Your website will simply not work until you do this.
Please note that we do not provide support for this and it is your responsibility to have this done before you approach us for support.

*delegation is the assigning of Name Servers to a domain name