You have a wide variety of descriptors to choose from, for the purpose of this tutorial we'll make the descriptor "Back Door"
Words are selected on page 32 of the Programming Guide.
The # key plus three digits will select a word
Pressing "6" will save a word in memory
Pressing "8" will end and save descriptors for the zone
"Back" is descriptor number 013
Enter # 013 then Press 6 to save the descriptor
"Door" is descriptor number 057
Enter # 057 then Press 8 to save and advance