Copy animation from one blend file to another blend file, which has the same mesh.

I have a human model with lip-sync animation. I have another duplicate model of the same. I have added some more lip-sync animation in the duplicate model. I want to copy those updated animation frames into the original model. Somewhere i saw, i need to use Shift + F1 to do this etc. But, i want step by step details, how to do this? How to open two blend files into one and do copy etc.

Can someone please guide me?


Appending tutorial

For animations, try appending the action. Then in the action editor select this appended action.