How include contributions to a manuscript of a paper in CV
As a student, it is entirely appropriate for you to list manuscripts "in progress." However, I would make sure that the manuscript is actually progressing before listing it on your CV. 

If it's in preparation, you then list it as you would any other publication, except where it's published (journal, volume, page, year), you instead list where you plan to submit it (if you know that):


  Author List (including you). Title of manuscript. To be submitted to Journal X.


or, if you don't know where it's going to be submitted:


  Author List. Title of Manuscript. In preparation.