In Main menu go to "Extras" than "Codes" and you can type in the passwords. 
If correct it will confirm at the bootom of the screen.

GM2OPEN8 - All Gamemodes 
A11T3AM5 - All Teams 
MAXSKILL - Max. Skills 
Z26BEXW8 - Micro Soccer 
E06J3CT5 - New Object in Inventory 
SPEEDY01 - Unlimited Turbo 
5Y104D9A - Unlock Streetballerteam 
WIMP_A.1 - Weak Opponents 

Tested on Pal-Version. Should work on NTSC too.