Mint comes with a screensaver.
Screensavers in Linux are not like screensavers in Windows. You don't go out and grab random screensaver programs from random places and install them.
You can open the Mint Software Center and search for "screensaver" and find the one that is installed. Its settings can be found somewhere in the Control Center, but I forget exactly where--I think under display, but it might be under power management or some other such category.
My recommendation is to remove whatever screensaver came with Mint (in my case, it was mate-screensaver, as I prefer Mint MATE to the other flavors) and replace it with xscreensaver, which is far superior to mate-screensaver, gnome-screensaver, and kscreensaver, all of which are lamer clones of xscreensaver with fewer screensavers and more limited configuration options.