If you happen to have a dev account.
You use the ~ tilde key. (IN GAME)
NOTE: (if you have a dev account and the console window does not appear and you have chat servers running)
You may have to type in the in game chat window:
/console
For Regular User
/accesslevel 0
For GM
/accesslevel 4
For Dev
/accesslevel 9
(only GM or Dev can access the console window)
If you had to type an acceslevel then repress the ~ tilde key at this time, otherwise it should already had appeared. (IN GAME)
Console drop down window appears.
Start to type a command and use CTRL-TAB to get a list of what is available based on what you've typed so far.
Pg-Up / Pg-Dn scroll up and down in the console window
Home / End goes to top or bottom of the console window