Depending on your Rendhat 7 installation you may end up by a default hostname localhost.localdomain. This hostname will be shown on various services your new server will offer as well a it will be show on your command prompt such us:
[root@localhost ~]#
To chnage your hostname simply edit vi /etc/hostname file and inlcude name of your host.

For example to change hostname to "rhel7" the /etc/hostname file will contain:
# cat /etc/hostname
redhat 7 linux change hostname
To update your command prompt simply relogin and to apply this change system wide it is recommended to reboot your Redhat server.