Dorayaki: Set the Portfolio posts 

Hello everyone! I’m trying to configure the posts in my “Portfolio” but every time I set “featured image ” you see a big picture in the header of muy post or this small square on top of everything. I just want it to be clean, with the thumbnail on the main page. I am new arming themes from WordPress, know how to understand. Thank you very much for the help from now on!

Example: http://florencialibertini.com/logo-florencia-libertini/