How can I add more images to Mate Screensaver???

[heavy metal]

Hi friends, I want to add more images to display when the Mate Screensaver activates, but I don't know where that could be, I want to know if I can just find the location and just drag n' drop the files and if the files have to be in a specific format, the files I'll be using are JPEG format, well I'll be waiting for someone to give me some advice, thank you for your time!