....by hand, over a rigid, round bar (steel scaffold) with lots of patience, stopping and checking. How experienced are you and what tools do you have?
Making good panels first time is a skilled process, so be prepared for a few wasted attempts and material.
You will need a few basic fabrication tools though to make the learning process easier.
As well as the art of bending, stretching, moving and folding metal It takes a lot of improvisation and preplanning, simple things that get overlooked such as how big the initial shape needs to be cut to allow for the bends and what needs folding/bending first.
Don't let it put you off though, a well made, properly fitting, homemade panel is highly satisfying and unhealthily addictive!
Depends what you have. With what I have I would start rolling the curve In my rolls, then flatten the bits required again before bending the flanges from the newly flattened parts.
Or buy them or get them made by a man with the skills n gear