Sorry...my bad for assuming newer software. This may help:
TO ASSIGN DID TO A SET (EARLY SYSTEMS)
1. Enter into programming by pressing Feature **266344 266344
2. The display reads “A. Configuration”. Press SHOW.
3. The display reads “1. Trk/line data”. Press SHOW.
4. The display reads “Show line:” Enter line number
5. The display reads “Rec’d #:none”. Press CHANGE (from the display) and enter DID.
6. The display reads “Rec’d #

DID). Press NEXT.
7. The display reads “Line Data”. Press SHOW.
8. The display reads “Line type: Public”. Press NEXT.
9. The display reads “Prime set:xxx” Press CHANGE (from display) and enter ext
10. The display reads “Prime set: ext”. Press HEADING three times.
11. The display reads “1. Trk/line data”. Press NEXT.
12. The display reads “2. Line access”. Press SHOW.
13. The display reads “Show set:”. Enter ext.
14. The display reads “Line Assignment” Press SHOW.
15. The display shows the first line assigned (or none). Select ADD (from display) and enter line number.
16. The display reads “Line xxx: Assigned”. Press NEXT two times.
17. The display reads “Ringing”. Press SHOW.
18. The display shows the ringing assignment for the first line assigned. If necessary, press NEXT until line 124 appears.
19. The display shows “Line124: RING”. Use CHANGE if necessary to find the desired ringing option.
20. Press Rls.