Once elected, a new President picks their Cabinet. The Cabinet is 15 department heads who advise the President and help run the country. George Washington’s Cabinet had just four departments: State, Treasury, War and Justice.
The President nominates the Cabinet members and then they are approved by the Senate. In addition to the 15 department heads the President may elect to elevate other administration officials to the Cabinet. Examples include the White House Chief of Staff, The UN Ambassador, or National Security Advisors. Cabinet members are constitutional officers and are in the line of succession to the Presidency.