Access to the admin is obtained through links containing a one-time passcode (OTP). These links are generated from within the server and expire within a couple hours of being issued.
Once opening the link, continued admin access is granted to that particular browser. If the browser cache is cleared, then the user will need a new admin link.
To create a new link, within the server run
lamassu-register followed by a name to identify the recipient or purpose. For example:
If sending the link to another device, send it over a service which doesn't auto-preview the link (and thus invalidate it). Signal and Keybase are good for this, or within codeblock formatting in Wire, Riot, or WhatsApp.