First of all, do some more Reading on the Concept of MVC first. You'll get there.
To your Question: For Resources that have to be used by several other Resources, Components etc. etc. you usually use a Service. In some cases a Helper is a good Solution as well. Template Engines like Twig for Instance can use View Helpers for rendering. But those should be very abstract.
Services should be managed using Dependency Injection. You could have a DI Container which then provides instances of the services needed and can be used to manipulate them.
The Symfony2 Framework has a good DI Container Component that you can use. They also have a good Documentation Article on the DI Concept I think.