There are many things that candidates do in the way of campaigning in American presidential elections. They include:
Attending fundraisers. Presidential campaigns cost tremendous amounts of money and candidates must attend fundraisers personally when the amounts being collected are very large. Big donors want to have access to the candidates personally.
Having campaign rallies. Candidates typically hold many rallies and other public appearances in states that are important for the election. They generally have a standardized “stump speech” that they give to try to energize voters in a given area.
Obtaining endorsements. Candidates will meet with important individuals (like governors) or organizations (like interest groups and media outlets) and try to gain their endorsements. A candidate who has many endorsements tends to look better in the eyes of the public.
Televised debates. These have been important in all campaigns since 1960.
Get out the vote efforts. These are not conducted by the actual candidates. Candidates have armies of volunteers (and some paid staff) whose job is to identify people who might vote for the candidate and to persuade them to support the candidate. If the people can be persuaded, volunteers also work to ensure that those people do turn out to vote.