Servers hosted by us are equipped by default with a preconfigured server administrator account. To use it, all you need to do is use your login name as your nickname (or login), and as for password, you need to use the password you filled in as the RCON password in the order form.
In order to log in as an administrator, in ingame server console (which appears when you press F8 or ~ keys), please set your nick as the same one you use for logging in to the GameCP panel (or for FTP connections). To do that, write the nick NEWNICKNAME command in the console and press enter key.
Then, type the command below:
(where RCONPASSWORD is the password you put in the rcon password field in the server order form)
Remember that you need to have your nickname set correctly for this method to work, as instructed above.
Now, once you are logged in as Server Administrator, you can do various things which were previously locked. The easiest way to manage your server is by the admin resource, which is started by default. You can access it by pressing the P key. It allows you to eg. see the list of currently connected players, give other players administrative rights, kicking/banning players, starting/stopping server resources, chatting with other admins, etc.