in this case I present a design of my page that is style.css, but I'm inserting a special design for a multiselect ... then that design requires that you download bootstrap-multiselect.css and bootstrap.min.css, but it what I want is that it only acts on a div on my page which is saved with index.php ... how could I link them?
One way you could solve this would be to expand your CSS for that div. Let's say, for example, that you give the WYSIWYG division an HTMLEditable ID.
You can point to that div with your CSS and all the CSS within that div.
The previous css will only apply to that div. So it's just a case of finding the correct CSS you need in that div.
Note that you may need to override / reset the CSS of that div to stop your bootstrap3 being applied to it.
You can use less to make it all easier.
Source: link
probably what you need to do is:
1.- Find out if there is not a file css that of the style boostrap for that component that you want to use in your project.
and / or
2.- Verify using the chrome or firefox "inspector" which styles are actually being used for that component and see what line and what file it uses, what others, you eliminate it.