You should first determine whether the existing checkpoint file(s) can handle the amount of SPOOLDS space that you are adding before you add them.
Insure that the checkpoint files and spoolds files are allocated on low impact volumes. You can have multiple spoolds files on the same volumes. However it is suggested that the spoolds files be on different volumes from the checkpoint file(s).
You can add multiple SPOOLDS files at one time with a REINIT command.
CA Spool Configuration - SPOOLDS Parameter