At the moment custom Poi can only be imported using iTunes File Sharing.
TomTom .ov2 seem to work but .csv files need to have the headers in a different order to what most other Sat Nav's use and can be found in online Poi databases.
With CP the order is Lat, Long, Name whereas Garmin and others, use Long, Lat, Name.
I use excel to manage my .csv Poi files so it is easy enough to change the column headers into the correct format for CP. It is also possible to convert the Garmin type .csv files into TT .ov2 using various Poi Editors but I have found there is a limit to the number of entries one can have.
It would be nice to be able to just import .csv files without changing the headers around.