How to edit "Why us" text?

Click on widgets menu in the Appearance menu in the dashboard menu.
It will take you to the widget page.
There you will see a box named Left Block above footer at right side.
Drag the text widget into the box.
Give Title and Text as per your requirement.
To achieve the design as in demo, put your text in “li” tags.
eg:

• This is text 1
• This is text 2
• This is text 3
• This is text 4

You can use your own format as well.
(You can add any availabe widget as your requirement)

Make sure you check here for any other queries..
DOCUMENTATION

Is there a way to limit this block to just 1 static post until I have more posts to display?

Oops I meant this about testimonials, not Why Us. I will repost.