The Senate and the House must approve the new Vice-President.
“Whenever there is a vacancy in the office of the Vice President, the President shall nominate a Vice President who shall take office upon confirmation by a majority vote of both Houses of Congress.” -— https://constitution.congress.gov/constitution/amendment-25/#:~:text=Whenever%20there%20is%20a%20vacancy,of%20both%20Houses%20of%20Congress.
Do you know who gets to select the VP?