We elect the members of the senate and house of representatives, whom, in turn cast their vote for President. Find out more on the electoral college here.
So, it is true the popular vote for President on election does not matter, however, your vote for the members of Congress does and also through the nomination of parties' candidates to the general election. Hopefully, the members you vote for have the same candidate in mind.
Find out more here, too.
How is the President really elected?
