Step one: mine and refine 30 quadrillion tonnes of magnesium on mercury (abundance of 12% in regolith)
Step two: launch said magnesium at Venus where it then burns in the atmosphere to form magnesium carbonate, magnesium oxide and graphite.
Step three: add redirect a comet or two
Step 4 : Add oxygen
Step 5: you now have a planet with liveable pressure, temperature, radiation and gravity. Profit???
How did we get jewed into mars?