I installed mate-system-monitor on my elementary OS Loki install via AppCenter, but I couldn't find it in the Applications menu. I searched for it, with no luck. So I uninstalled it, and installed it again in my terminal.
$ sudo apt update
$ sudo apt install mate-system-monitor
It installed propperly, so I searched in my applications menu but still couldn't find it. So I tried launching it from terminal.
$ mate-system-monitor
It worked partly as it opened up the monitor and the monitor worked fine. But the terminal showed errors.
Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap"
Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap"
Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap"
Gtk-WARNING **: Unable to locate theme engine in module_path: "pixmap"
Gtk-Message: Failed to load module "pantheon-filechooser-module"
** (mate-system-monitor:6768): WARNING **: SELinux was found but is not enabled.
I fixed the first 4 lines by following these, but how can I fix the last 2 lines and also be able to find the monitor in my Applications menu? (I tried uninstalling and installing again, but it didn't work.)