Answer:
Step 1
The House of Representatives holds a few hearings, then they vote to impeach the President. If the House of Representatives votes in favor, by a majority, the House sends Articles of Impeachment to the Senate.
Step 2
The Senate starts a trial of the President to decide if the President is guilty of the crimes charge in the Articles of Impeachment. If 2/3 of the Senate votes to accept any Article of Impeachment, the President is automatically removed from office and the vice president takes his place as the new president.
*So far, no president has been impeached.