What does ratify the constitution mean?
Ratify the Constitution means to approve it. The Constitution required nine of the 13 states to approve it before it could be ratified.
The word ratify means "to pass, or approve". So, you're essentially asking which article of the constitution tells us how to approve the constitution and make it law. I think what you mean is "What article tells us how to amend the constitution." To amend the constitution means to somehow change it, which has only happened 27 times. Article #5 tells us how to amend the constitution.