Where is the ratification process found in the constitution

the ratification process started when the Congress turned the Constitution over to the state legislatures for consideration through specially elected state conventions of the people.

The Congress, whenever two thirds of both Houses shall deem it necessary, shall propose Amendments to this Constitution, or, on the Application of the Legislatures of two thirds of the several States, shall call a Convention for proposing Amendments, which, in either Case, shall be valid to all Intents and Purposes