“The President, Vice President and all civil Officers of the United States, shall be removed from Office on Impeachment for, and Conviction of, Treason, Bribery, or other high Crimes and Misdemeanors.” – Article 2, Section 4
Step one: the House of Representatives by simple majority passes Articles of Impeachment, laying out the alleged offenses of the impeached officeholder. Step two: the trial is held in the Senate. In the case of the president, the Chief Justice of the Supreme Court presides, otherwise the President of the Senate aka the Vice-President. (The Constitution does not specify; inferring it would be the usual presiding officer.) A two-thirds majority is required to convict and remove from office. Conviction by the Senate does not disallow criminal prosecution.
