The Traditional French Market on Kampa (Francouzský Trh) is an annual event – at the west end of Charles Bridge. That’s the side of the bridge that’s away from the city center. Just cross the Charles Bridge, go down the steps, and there you are.
This is the (zoomed-in) view from the Charles Bridge. It’s not far. I don’t have a fancy camera – it’s one of those pocket Canon PowerShots.