Players agree to the number of rounds needed to win the game before game play starts.
On the first throw, the dice with the highest number rolled is put to one side. If two or more of the dice show the highest number only one is kept for the next throw.
On the second throw the remaining two dice are thrown and once again the highest-numbered dice is put aside.
The final dice is then rolled.
The player with the highest score wins the round.
Ties are broken by additional rounds of rolling
This is from https://bicyclecards.com/how-to-play/going-to-boston/.