To enter the codes you have to get a fax first. Press the green ? button that shows up from time to time at the bottom of the screen to get to it. Then just use the mouse to press the numbers on the fax machine and press the send button.

F11 = Level lose
F12 = Level won
7827 = After you win the level go to a rat shoot level
24328 = Enable the following codes during gameplay
CTRL+E = Makes one emergency
CTRL+C = All research completed
CTRL+S = Doctor with special stills
CTRL+Y = Skip to the end of the year
CTRL+M = Skip to the end of the month
SHIFT+C = Get $2000
SHIFT+1 = Extra patient
SHIFT+I = Change patients illness

To start on a specific level use this command line switch: -Lx Where x is the number of the level you want to start on.
After typing 24328 at the fax, when playing normally press Ctrl + Shift + C. This will give you all items. We have tested it + it works