The way in which major political parties formally select nominees for the presidential election is through the national convention. The national convention is a large gathering of party delegates from across the country, where they come together to choose their party's official candidate for the presidency. During the convention, delegates vote on the nominee, and the candidate with the majority of votes becomes the party's nominee for the upcoming presidential election. This is a significant event in the election process, as it solidifies the party's support behind a specific candidate and sets the stage for the general election.
The way in which major political parties formally select nominees for the presidential election is through the national convention.