@0 KCI is a way to keep the conductor away, when you don't want to talk. With the ticket imported in the DB app you have a "check-in" button (or similar) in the details - simply enter wagon and seat number. With this done the train staff will know that you have a valid ticket and should ignore you when checking the passengers. In newer/modernised ICEs even the seat display will show that is it taken.
@foobarblubb@0 disclaimer: KCI may be broken at any point in time and therefore u may still experience manual ticket checks by your local conductor:tm: