That’s the easy part. What happens when the person with the most votes doesn’t have a majority?
RCV ballots are counted in a series of rounds, as shown here.
First, all the first-choice votes are counted, and if any candidate has a majority (more than half) the votes, that candidate wins, just like in our elections right now!
Otherwise, the last-place candidate (with the fewest votes) is eliminated. Any votes cast for that candidate are instantly transferred to the next preference indicated on each voter’s ballot (if the voter chose to rank more candidates).
After each round of counting, we check again to see if any candidate has won a majority. If not, step 2 is repeated until one candidate achieves more than 50% of the vote and wins.
https://www.cbsnews.com/news/ballots-destroyed-suspected-arson-boston-dropbox/