How to access Vertexdata in shader?

I am trying to write a global shader (vertex and pixel shader) with a custom pipeline.

I understand how to send the mesh data to draw using mesh proxy and send it for rendering in UE4 pipeline.

But I want to how to I access this vertex data in a vertex shader? For example if I write a custom FVertexFactory and attache the buffer there but how I do I access this data in the shader?

To give some more context - UE4 Cable Component class - I see how the buffer are attached and filled. But is there a way I can access the vertex data in a shader? My requirement is to do some compute in the vertex shader (like decoding etc)?

Any sample or hints on how to pass the data from MeshFactories and access it in the Vertex Shader would be appreciated.