How will we know who the Messiah is?

I know about the prophecies, but how does the Messiah figure out who they are? What if multiple people claim to be the Messiah at the same time (especially in the age of social media, I’d bet good money several people will be claiming to be the Messiah once the first person claims such)? What do we do once they gain popularity? Rebuild the Temple? How would we know exactly where to do it and how would we work around the Temple Mount?

I might think of more questions later, thanks for any answers