How do we get Indices for glDrawElements()?

I'm trying to use the Assimp library to import models to a rudimentary OpenGL application with VBO use.

If I understand it correctly glDrawElements is one of the ideal modern ways to draw things.

But how do we get that information from a generic import library?

If you have specific Assimp library knowledge it's appreciated.

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What is generally the process to generate these?