Here is a complete instruction:
To use the codes, you need to activate the console. To do this, find the autoexec_a1.cfg file in the game directory, in the profiles folder.
Open it with Notepad and add the following line to the end of the file:

setvar dev_console_password = schwinge-des-todes

The end of the file should look like this:

//==================================
// Startup
mainmenu
setvar dev_console_password = schwinge-des-todes

After that, you will most likely need to add the following line to the input_a1.cfg file:

bind show_console '`'

so that the game knows what console is and it looks like this:

// obsolete, but strictly need for compability with some interfaces
bind close_window 'ESC'
bind confirm_action 'ENTER'
bind confirm_action 'NUM_ENTER'
bind show_console '`'

After that, the console will work. The line bind show_console '`' must be added to two files (input_a1.cfg), the first in "Heroes of Might and Magic V/profiles",
the second in "C:/Documents and Settings/Owner/My Documents/My Games/Heroes of Might and Magic V/Hammers of Fate/Profiles/Owner" (Owner is the account name)

The console will work, but the codes won't: