Well, humanity must terra form both Mars and Venus

The project can be funded by harvesting all the asteroids in the belt. The estimated worth of all the metal in the biggest one is over 100 trillion dollars

The asteroids can be pushed to mars for processing and for adding mass to Mars

All the small ice moons of the gas giants can be moved to mars and harvested. So can Saturns ice rings

Ceres can be pushed into a Mars orbit

Once Mars has more mass from water and asteroids it’s atmosphere can be built up by moving vast quantities of CO2 from Venus to Mars and nitrogen from Titan

Giant reflective mirrors orbiting mars can focus sun light in Mars to help heat it up

Once enough CO2 is removed from Venus it will cool down quite a bit. To help with cooling Venus giant reflector satellite mirrors can keep heat and light away from Venus’s atmosphere

Small ice moons can be crashed into Venus to add large quantities of water

Humanity can help reshape both Mars and Venus for humanity