Function "download picture"

Hello, I dont really know if this is problem of template or plugin but I would like to have website where are pictures and under them will be button for view and download like here: templates.com/product/powerpoint-templates/

Does somebody know how do it? If find the right template or plugin? I am beginner in this area. I know wordpress and use it for my blog but I dont know much about editting template.

Thank you very much for every help.
Catalin