For terminology and schematics see here: Turnout Schematics and Bending (bentley.com)

To create a new feature definition, copy an existing one single, double, crossing single slip, crossing double slip, etc
You can place a turnout to get a feature definition in you file.

Then set the value through the properties dialog. You must at least know the ratio or angle (angle = tan-1 (1/ratio)), mainline length and triangle length.
Then you must connect geometry from Theoretical .1 to .3
All elements will be tangent except if you set a ratio at .1
If you know the elements that fit, you just have to set the number of elements and enter the value.
If you don't know the elements, you can design using geometry tools or calculate the average radius: R = Tangent Length / tan (angle / 2).
Tangent Length is the minimum between .1 to .0 and .0 to 3
If .1 to .0 is less than .0 to .3 then radius first (L = angle * Radius) then straight length = triangle length - tangent length
If .1 to .0 is greater than .0 to .3 then straight first