If you mean this plugin : https://devot-ee.com/add-ons/ctrls
I have used this before. the file you get is called
ext.ctrl_s.php, and you should install it here
I've just installed this on EE 2.10.1 to test and it works fine. AS mentioned you need to goto
Add-Ons > Extensions and 'Install' it.
Of course, I've done nothing but expand on Robson's answer above, except I've gone and got the extension for myself to check (assuming I've referred to the right one!). Once you get it working, make sure you mark Robson's answer as correct!