The programming instructions for labelling zones on a PK5500 keypad are found in the keypad manual (not the main installation manual). They are a bit vague, so to summarize the sequence would be:
001 (for zone one, 002 for zone 2 and so on, must be 3 digits)
XXXXXXX Label XXXXXXXX (see below for instructions to change the label)
Then the next section.
When done, use ## to exit programming
To change the label, use the arrow keys to move the underline to the character that needs to be changed then use the numbers 1-9 on the keypad to choose the number. Each time you press the number you change the leter as outlined below.
 A,B,C,1 D,E,F,2