Which Ronaldo?
Cristiano Ronaldo?
Ronaldinho?
The other Brazilian ronaldo?
I'll assume you mean Cristiano.
He kicks it with the top of his foot. With the laces. His
technique is unique because he pulls his kicks in a "swiping"
motion making spectacular curls. Like the one against
Portsmouth.
Go on YouTube and look for "Cristiano Ronaldo freekick vs
Portsmouth"