Homepage Introduction block appear just below the slider on homepage.
This region acts as a Drupal block region. You can create this block from:
Administration >> Structure >> Blocks
Navigate to: Administration >> Structure >> Blocks and click Add block
Create a new block with some content. You may use below sample content.
<h1>what we do!!</h1>
<p>We design beautiful high quality Drupal themes</p>
Hint: Use Full HTML as Text Format.
And set location of this block to Homepage Header region and click Save blocks.