You select first, second, third choice - and they get counted.
https://www.fairvote.org/rcv?gclid=CjwKCAiAnvj9BRA4EiwAuUMDf_jEiexXGtGiwM25A2RGuAVCkXpQkmmVC4w6wt1YuyJ_usboAZawyhoCPnwQAvD_BwE#where_is_ranked_choice_voting_used