[Plugin: Camera slideshow] Problems with activating

Hello,

I’m a new user of WordPress, so I’ve tried, but I don’t understand everything about the .php-files yet. The installation text of this camera slideshow says something about ‘function.php’, but my theme doesn’t has that file. I installed the plugin and activated it, so the symbol is visible when editing a page or post. Is this enough to use this slideshow or should I do something with the .php files? At this moment I can’t (or I can’t find how to) insert pictures…

Can someone help me with this?

https://www.ads-software.com/extend/plugins/camera-slideshow/