Q:

How to enable Library in Drupal 7?

I have installed the module and also cleaned the cache. I have read hundreds of tutorials and yet, I'm still stuck. I have upload the files in /sites/all/libraries/jqmulti and yet, there's nothing.
See screenshot:

A:

From your screenshot, that module isn't enabled. After you enable (check the tick box) and save, re-visit the modules page. There you should see a "Settings" URL next to your enabled module that will allow you to edit as needed.
Reading the module description, I should warn you that loading two versions of jQuery could cause issues with functions firing twice
Edit: Looking at the picture again, this module also requires that the "Libraries" module is enabled. At the time of your screenshot, that module was disabled. Please make sure the tick box next to the libraries module is added as well

