how to apply skins o windows forms

You need to learn more about Regions and paths. The way you apply skins on Windows Forms is, you create a Path with say wired looking shaps like an oval shaped with ears and nose and then create a Region from the path and set Form.Region property to this new region. It will make your form look like a region.

Here is an example:
http://www.c-sharpcorner.com/UploadFile/jibinpan/ShapedForms10172005012018AM/ShapedForms.aspx

Search this site (not forums) for Shaped forms to get more sample code and articles.