Many of our patterns will come with collars that need to be sewn to the blouse bodice. Here is one tutorial that has chockful of information to guide you through the process.
This document is courtesy of New Mexico State University's Department of Home Economics.
Here is a list of videos that use some of the techniques discussed in the document above. It focuses on a traditional man's collar without the collarstand and a separate front facing piece.
Here is an alternative to attaching a collar to a blouse that has a grown-on buttonstand and a more feminine rounded collar.