On the Unravel Server, open /usr/local/unravel/etc/unravel.properties with vi.

sudo vi /usr/local/unravel/etc/unravel.properties

Append comma-separated usernames to the value of com.unraveldata.login.admins. For example,

com.unraveldata.login.admins=admin,admin1,admin2

Restart unravel_ngui service.

sudo service unravel_ngui restart