Why the image can't show in search result?

In Adventure Journal Version 1.7.2, there is diffrent
(1)http://vothanhnha.com/category/tranh-theu-chu-thap/tac-pham-tranh-theu/
And
(2)http://tuphung.wordpress.com/category/tranh-theu-chu-thap/tac-pham-tranh-theu/

I need to show image like (2)
Please show me how?

Thank you!