Without knowing what you are trying to achieve and what difficulties you've encountered it's not possible to say. Have you tried the tools in the editor? If you mean what tools do you use to bend real rails, then I've seen it done by a gang of men with crowbars.
Is it possible to create a rail defined by a type, a length and a radius of curvature? The last 2 parameters are values to be specified numerically in advance.
Use the blueprint editor to create a custom track or TS tools to edit a copy of an existing track, you can then set your bend radius at tight as you want.