If you're wanting to add yourself as an admin on your Rust server, follow these steps:
1. Via your 'Web Console' or RCON, type this command: ownerid 76560000000000000 (replace this SteamID with your SteamID. You can find this here
2. After you've done this, ensure to type the following in your 'Web Console' or RCON: server.writecfg
3. If you're currently logged onto the server, simply reconnect and you should have your admin permissions.