1) You exchange CP for a Custom NPC... See CP Exchange for requirements.
2) In addition to obtaining a custom-race/appearance/gender/name companion with basic skills, who can level and potentially attack with you (not sure if this is re-enabled or not), you are able to Script an interaction with the Custom NPC. Mostly it's for RP purposes.
Many options are listed on the Support Page (Green X+ button next to CP on the Sidebar)
Additionally, the Work for CPs forum sometimes has small projects that you may be able to contribute to and potentially gain CP for.
Finally (and this requires a significant amount of time, commitment and sometimes OOC skills), volunteer for one of the Teams that currently have need of new members. Hiring/Team Needs are usually posted to the SimNews:Community News and vary significantly in the CP compensation they provide.