Hello.
This is not a support forum for hosting customers, only for support for Directadmin license holders, so admins.
You should ask your host for support, since every host can configure things in his own way, which is also a reason we can't be of help.
And next to that there are other forums for general help like webhostingtalk.com and similar.
To be a bit of help, for hostname, try localhost
and if that does not work, contact your hosting company for support.