Categorizing or tagging cards is a feature available via the "add note" field on the cards you scan. All you need to do is use "hashtags" to add the categories you'd like to search for, or ingest into your CRM.
For example, if you add #LEADS as part of a personal note to a contact card, you can:
Find all #LEADS tagged cards by typing '#LEADS' into the search box at the top of the app; or
Filter, or ingest the category into your CRM via an integration or a CSV export
To add a personal note:
Tap the card you want to tag/categorize
Tap 'Add Note' at the bottom section
Type #TAGNAME in the 'Notes' box