A good DI implementation should enable DI on any object, regardless of the latter being DI-agnostic or not.
Prism is a bad example, as the last time I used it (2 years ago) it required objects to be DI-agnostic by enforcing use of the [Injection]
attribute. A good non-DI-agnostic example is Spring Framework (extremely popular DI framework for Java, has a .NET port called Spring.NET), which allows enabling DI via so-called context files - these are xml files that describe dependencies. The latter need not be part of your library, leaving it as a completely independent dll file.
The example of Spring can tell you that you should not have any specific configuration, prerequisites or patterns to follow in order to make an object injectable, or allow objects to be injected to it, besides the programming to interfaces paradigm, and allowing programmatic access to suitable constructors and property setters.
This does not mean that any DI framework should support manipulation of plain CLR (.NET) objects, a.k.a. POCO-s. Some frameworks rely only on their specific mechanisms and may not be suitable to use with DI-independent code. Usually, they would require direct dependency on the DI framework to the library, which I think you want to (and probably should) avoid.