To add yourself or other users as an admin follow the steps below.
1. Go to your Control Panel. Stop the server, then click on the 'Configuration Files' button.
2. Once you're in look for the 'serveradmin.xml' file and hit [ Text Editor ]. Usually at the last part of Configuration Files.
3. Look for the following parameters below. You should start at line 52 where you will see the </users>
<adminTools>
<!-- Name in any entries is optional for display purposes only -->
<admins>
<!-- <user steamID="76561198021925107" name="Hint on who this user is" permission_level="0" /> -->
<!-- <group steamID="103582791434672565" name="Steam Universe" permission_level_default="1000" permission_level_mod="0" /> -->
</users>
4. Add the following line in between the <admins> and </admins> for Steam admin (Find your SteamID64 using this link: https://steamid.io/lookup):
<user platform="Steam" userid="YourSteamID64Here" permission_level="0" />
or add the following line for an Epic admin:
<user platform="EOS" userid="YourEpicOnlineServicesIDHere" permission_level="0" />
FOR SERVERS RUNNING BELOW ALPHA 20.4, ADD THE FOLLOWING LINES:
<admin steamID="76561198081237071" permission_level="0" />
5. Click save, and start your server, you should now be admin.