The Miami Heat are going to need help if they're going to win the Giannis Antetokounmpo sweepstakes. They're not going to outbid all the potential suitors, and the only real way they're going to land Giannis is if the Heat emerge on the (extremely) short list of his preferred landing spots.
Giannis would, essentially, have to tell the Bucks that he wants to be traded to Miami, and perhaps only Miami. Even then, as we saw with the Damian Lillard sweepstakes, there's no guarantee that Milwaukee would even oblige.
However, it does appear as if that's the only clear path toward the Heat finding a way to win the Giannis sweepstakes.