This is simple coding, if your news are populated from database, then each news should have uniqe ID (primary key) in table. Make one more table in databse "Comments". Add columns like comment id, Name, email, comments etc (whatever you wanna ask from user). Add news id (as foriegn key) in your comments table.
Make a form in your asp.net web application e.g. textboxes for name, email and comments where you are showing news. When you will load news from database, you will have news id. If user will add comments, save his/her comments and with news id as foriegn key.