first webmin installtion & proper dns setup

hi,
i’m planning to install webmin on centos7 , in godaddy i have ns1.mydomain.com & ns2.mydomain.com set up for dns. after a bit of research i’m still not sure how to set hostname (server.mydomain.com) for my server, where, when & how exactly can that be done ! in webmin or godaddy .

ps: www.mydomain.com will also be a website hosted on webmin.

Regards