Cambiar el idioma predetermidado del Tema

Hi, I have the pleasure of having his theme for my WordPress site.

Please I need your help to suggest me how I can make the language is Spanish?

How I can install a slider that muetre outstanding images of the recent post to climb to blog?

The site I’m putting http://www.ondacultural.org comes from, so soon I would start with a similar product which has been used in the past, in the future I intend to take full potential of its magnificent subject.

Thank you for your attention.