Just to confirm what to do and where to find it...
Menu 4 (Core Maintenance, was Brooms Maintenance for those without the newer Core updates).
Choose "Chaser Sequence Maintenance"
In there are all the options you'll need but to get you started pick "Create Sequence". In the next box, choose a code (up to 4 characters) whihc will specify the purpose of the chaser sequence, sor "RD" for example.
The next screen lets you choose the sequenced letter and how long to give each one a diary period for. You can choose up to 10 chasers (do not pick the first letter in the sequence though).
Once this is done, the user will choose the chaser sequence when creating the initial letter. Chasers are generated from the Diary or Letter Generation menu (menu 3).