270 votes are required to win the Presidential election
Each state has a specific number of electors, which the number of these electors is determined by the number of Congressional Representatives for that state. Of course, DC isn't a state, and it has been awarded 3 electors.
Basically, these assigned electors cast their votes as to whom they want to win, in accordance with the popular vote in their respective states.
So, when you vote, you are voting to win over the popular vote for your specific state, so the electors of your state will cast their vote in your favour.
Whether 2 people vote, or 2 million people vote in your state ..... only the designated number of votes will be cast for the Presidential election.
So, your vote doesn't count accumulatively .. but, it does count to win the popular vote in your respective state.