You need to fill in your Title, Keywords or Description boxes in the Page Properties section. In your particular case, the Description box is what fills in the Facebook description.
I also went ahead and re-scraped your page through the Facebook debug tool: https://developers.facebook.com/tools/debug
The last scrape was from 14h ago and it had the “This content…”. Now the re-scraped link has “Es momento de…”
Any link you post forward should have the new meta information.
*EDIT* You might also want to take a look here: http://documentation.unbounce.com/hc/en-us/articles/203660994-Social-Widgets#content9 for a bit more details on optimizing your pages for social sharing.