First you have to create some CAR Keys.  You can do this by going to memory block 1-2-04.  You can only create 4 CAR (SIE) keys at a time.  It's a good idea to start your CAR Keys using the last ports (starting from C0) in the system and work your way backwards.  Once you created a block of 4 CAR Keys in 1-2-04, go to memory block 4-10 and program extension numbers for these CAR keys.

Now to add these CAR Keys to a phone, go to memory block 4-12 and program these CAR Keys (SIE Keys) on the phone ports that you want them.  Be sure that when you program a CAR/SIE Key on a phone you remember what the port# of the CAR/SIE Key was.

To get these CAR/SIE Keys to ring on the phone that you added them to you must go to memory block 4-37 and go to the port of the phone that they are on.  You can program the line key that the CAR/SIE Key is on to ring on delay,immediate, or no ring.  This memory block 4-37 is for Day Mode ringing.  4-38 is Night Mode ringing.

Probably best to follow along in the manual when reading this.  Goto Chapter One Section 3 - System Data List.  These pages will help you to get familiar with how the manual is laid out.

Another newbie

This business of CAR keys - does that only apply to certain systems or all.  I'm mainly interested in small system programming 120s and the like.