Which part of the legislative branch would vote to impeach the president?

When the Constitution was being written, there was a great deal of debate about the amount of power the President would have. Some people feared that giving the President too much power would cause problems. To deal with these concerns, the process of impeachment was added to the Constitution. If the President breaks the law, he may be impeached. In the words of the Constitution, “treason, bribery, and committing high crimes and misdemeanors” may result in impeachment.
There is a process for impeachment. The House of Representatives would investigate to determine if there is enough evidence to impeach the President. Thus, the House of Representatives would vote to impeach the President if the members of the House of Representatives believe that enough evidence exists to warrant an impeachment. However, impeachment doesn’t mean the President is guilty of the charges. If the House of Representatives votes to impeach the President, the Senate would hold the trial to determine if the President would be removed from office. If two-thirds of the Senate votes to convict the President, the President would then leave office.
https://www.thoughtco.com/impeachment-the-unthinkable-process-3322171