After converting a mesh to a curve , how to have a smooth curve? i have converted a square mesh to a curve , so i have a really narrow agle i didnt find any way in the curve editor to modify that , and i cannot change the handle of this cuvre ..i just want to transform this thoses line into real curve but they stay straight ...

is there a way with a converted mesh; to modify the lines into a real curve ?
In the left menu (displayed with T) > Tool > Set Spline Type > Bezier