Step 1: Recreate da Vinci's environment as closely as possible as a computer simulation.
Step 2: Assign a good guess as to what da Vinci's genes would have been.
Step 3: Simulate his life.
Step 4: Compare the output of his simulated life with his real output.
Step 5: Mutate the DNA, keeping any improvements.
Step 6: Until simulation is "close enough", goto 3.
Step 7: Instantiate DNA as a real human.
If the environment were perfect, we could get arbitrarily close to the real da Vinci. And if we had even faster computers, we could get arbitrarily close to a perfect simulation of the environment (which I leave as an exercise for the reader).
I'm going to waive the ethical considerations of steps 3 and 7 in favor of linking here.
