Import your users into CB first before bothing to import with CBSubs as you can't import at the same time. Once imported into CB navigate to your database and export as CSV (you really only need to export userid column), then format to your needs for import into CBSubs.
For assistance with
CB Juice
please contact the developers, it is not a development of the CB Team.
Accounting history? There's history of all purchases, subscriptions, etc... that you are welcome to present to your accountant.