Assigning speed dial buttons to a feature access key is basically a two step process:

step 1:
program telephone number to a speed dial bin.

Each station can have 20 personal speed dials, with bins numbered 00 - 19. I usually make up a cheat sheet for each station with column 1 being the speed dial bin, column 2 being the Telephone Number, and column 3 being the name associated with the telephone number:

Press [Feature]/[FNC] (depending on model of phone)
press [Redial]/[LNR/SPD] (depending on model of phone)
dial the desired speed dial bin (00 - 19)
dial 9 (trunk access code for system to grab outside line)
enter the telephone number (24 digits max)
Press [Feature]/[FNC]

Step 2:

Assign the speed dial bins to feature access keys.

Press [Feature]/[FNC]
press [Redial]/[LNR/SPD]
press desired feature access key to be programmed.
Dial 0
Dial speed dial bin ( 00 - 19)
Press [Feature]/[FNC]

"I didn't do it, and I won't do it again"