Change lockscreen in MATE?

I want the lightdm-webkit-greeter to be mine lockscreen, do you know how to change it? I found a way how to add Xscreensaver screensavers to mate-screensaver or even change background, but no word on how to change lockscreen completely.

EDIT: Just to make it clear: I use lightdm-webkit-greeter for login and it works, but when I close the lid, the mate-screensaver-command -l is executed - which I want to change it to lightdm-webkit-greeter aswell using dm-tool lock.

If you want lightdm you just have to install it: sudo apt-get install lightdm. During the install, you'll be asked to select your default display manager. Select lightdm.

If lightdm is already installed, run sudo dpkg-reconfigure lightdm.