Sketching component does not provide an API.
    Use following steps to create sketch based shapes
  • In the Part Designer, add one of following feature
    • Sketch Extrude
    • Sketch Revolve
    • Loft
    • Bridge
  • Open feature editior(it will automatically open when you add new)
    • Click on the pencil icon for editing sketch. This will launch sketch editor
    • Add variables and reference them to set dimensions or constraints.
    • Click on edges to see length, radius etc
    • While using constraints, first set the longest length, angle constraint and then successevile add other constraints
  • Click on wheel icon (settings) to edit position and orientation of the sketch plane. This is rather important to remember. You are adjusting sketch position relative to other shapes using feature's smart alignment tools. Use the plane editor settings to position and orientation of the sketch plane.

This video shows how to use sketch editing.