Sharing my shop on social media, how to edit the post design? (1.7)

[Pengus]

Running version 1.7.2

When I share my shop on social media (only tried Facebook so far), this is how it looks.

It just fetches the pictures from my slider, and that text says translated to english;

"Show "Ecommerce softare by PrestaShop" in footer"
What? Where did it get that from?
 

Is there a nice way to edit the looks of this? Maybe some module?

Edited September 25, 2017 by Pengus (see edit history)

[KenJiNx]

http://prntscr.com/gpw2xp

[Pengus]

Thank you so much, that fixed the text!   

So is there any way to set a custom image as preferred on social sharing?