Thanks for the reply.
Not sure whether I got the idea correctly. In the body of the document, I typed the word Chapter at the beginning (instead of putting a setting for automatically adding "Chapter" before the number). In the next line I typed my chapter name and made it heading 1. So now it appears as

Chapter
1
Introduction

Now, how do I merge the word "Chapter" with "1" visually? I tried pressing "alt+enter", but it does not bring them together.
Could you please clarify this?