Manage admins & moderators of and ARK server is pretty simple, you just need to get the right Steam64 of a player !
1 - Be temporary admin by password
Into the GameUserSettings.ini config file of the server, an administrator password is defined by default. You can find it at the line :
ServerAdminPassword=X
You can use admin commands thanks to this password by entering the following command in your console game :
enablecheats X
You can then enter server commands into the ARK game console.
2 - Get the Steam64 of a player
Le Steam64 ID allows the server to recognize a player configured as admin or moderator.
The simplest way to get it is thanks to the Steam Community website. Indeed, each player as a profile page which address is formatted like :
http://steamcommunity.com/profiles/X
The X part in the address corresponds to the Steam64 of the player, which is precisely the ID you need to get to put it as admin on your ARK server.
3 - Add a permanent admin
Giving the administrator password to any administrator of an ARK server isn't a good thing. The game has its own admin system that allows you to add Steam64 that you want to be considered as admins.
Create the following file on your FTP if it doesn't exist :
ark/ShooterGame/Saved/AllowedCheaterSteamIDs.txt
Inside, you must enter the list of Steam64 to who you want to give admin rights, 1 Steam64 by line and of course by player.
The modification will be applied at the next reboot. In case the server writes the file when it stops, you can do the modification after having stopped the server.