To enable console open Main.ini file located in the game folder and under section [GAME] is entry "DEBUGMODE = 0". Change value to "1" (without quotes). Save the file.
Now you can open console in-game by pressing [Shift]+[~] keys.
To enable cheats open the console and type in "g_cheats 1". Now you have enabled cheats.
[I] - God Mode
(supplied by: merrowind)