The manual says to press button #1 the same number of times as the first number of the security code and button #2 the same number of times as the second number of the security code etc. Note buttons 1-5 are below display.
ie for security code 3212
a) Press pre-set button 1 three times
b) Press pre-set button 2 two times
c) Press pre-set button 3 one times
d) Press pre-set button 4 two times
e) Check that the PIN code shown on display is '3212'
e) Press pre-set button 5 to activate PIN code.
grumpy
November 2013