Entering admin commands
The full list of ARK: Survival Evolved console commands is on the official ARK wiki at ark.wiki.gg/wiki/Console_commands. For each command it says what it does and what it needs after it (its arguments).
First turn on admin commands for your character with enablecheats and your admin password: see How can I make myself an admin on my Ark Server?
Then type commands in the console bar (Tab), as the wiki shows them. Upper and lower case don't matter: the capital letters on the wiki just make them easier to read.
On a multiplayer server most admin commands need cheat (or admincheat) in front of them. For example, cheat fly lets you fly, but just fly does nothing. The wiki shows whether a command needs it.
From the control panel's Console tab, commands go to the server as an admin: leave out cheat there.
Player IDs (kicking, banning, whitelisting)
Commands such as KickPlayer, BanPlayer and AllowPlayerToJoinNoCheck need the player's ID, not their name. To see each player's name and ID, enter cheat ListPlayers in the game, or ListPlayers on the control panel's Console tab. Copy the ID exactly as it shows: for Steam players it is usually their 17-digit SteamID64 (such as 76561198000000000); Epic Games players, and players on a crossplay server, can have a 32-character ID instead.
For example: cheat BanPlayer 76561198000000000
ShowMyAdminManager
ARK also has an admin menu in the game, where you can run many commands by clicking. They are the same commands as on the wiki, though some have slightly different names in the menu.
Turn on admin commands with enablecheats first. Then enter this in the console bar (no cheat needed in front):
ShowMyAdminManager
Even if you use the menu, check how a command works on the wiki at ark.wiki.gg/wiki/Console_commands: some commands have limits you can't change, and the wiki explains why they don't work with certain values.
Need help? Open a support ticket and we'll take a look.