That will happen when a human sets foot on the surface of Mars. Probably sometime in the 2030’s.
Did you know the Moon was inhabited by astronauts? Yes. It’s true. When they landed on the moon they had to stay several days before taking off again. That means they lived on the Moon and thus inhabited it for a short period of time.
The same will go for humans on Mars except they will likely have to stay longer because it takes about two years for Earth and Mars to be close to each other in orbit for a return flight.