Im exporting some animated models from Blender to Unity3d, but even when Unity sees the animations (I can play them), in the inspector, the Animator component of the object shows an error: Not initialized. And neither can use the animator in code to play animations. The attached image shows the error, which I think it is not the same I find when I google about Animator not initialized. How can I solve this?

By the looks of that image, you have no controller attached. Checkout this section of the manual.

If things still don't play, make sure you've configured everything in Unity's importer correctly (if you are using Mechanim, you must link the bones up correctly).

Yes, seems that was the problem. Added one and the message was replaced by another, but still have no idea about how to use it.