I've done 3 articles on this subject, and every time I visit it some new layer pops up. But I think as for any sitting member of Congress, section 3 is easy - expel and disqualify. Should be able to be done on a simple majority vote. For Trump and others not presently elected, I suspect Section 5 is required...passage of legislation. Here's the best Annotated source for the Constitution, currently set to begin at Section 3 of the 14th: https://constitution.congress.gov/browse/essay/amdt14_S3_1_1/