... correct and that is why the bill Barney Frank proposed in 2000 was a “bill to amend the Constitution...
H.J. Res. 88: A CONSTITUTIONAL AMENDMENT TO ALLOW FOREIGN-BORN CITIZENS TO BE PRESIDENT
ALL Constitutional Amendments start out as “bills”, that is how it works. If they can get the bill passed, they can then send it on to the states to be ratified as an amendment, just as the Civil Rights Act of 1866 became the 14th Amendment. They had to get the bill passed first and then introduce the language of the Amendment they wish to add.