At the title screen, go to game setup and hit start. At the bottom of the list of options, you can enter passwords. That's where you enter the following:

Password	Effect
QQXRB	Start game at level 11.
W26RJ	Start game at level 16.
DSZDD	Start game at level 21.
LKSX5	Start game at level 26.
D1H4R	Start game at level 31.
D1BTP	Start game at level 36.
R53HR	Start game at level 41.
BQYSZ	Start game at level 46.
4KLX8	Start game at level 51.
8WNPY	Start game at level 56.
FFGMS	Start game at level 6.
DXXLG	Start game at level 61.
1V4J4	Start game at level 66.
LF2LK	Start game at level 71.
JSDJY	Start game at level 76.
CWSPU	Start game at level 81.
TLZ5H	Start game at level 86.
1NY1H	Start game at level 91.
JZRUT	Start game at level 96.