Indexing is as simple as:

var post = new Post() { Id = 12, ... }
var status = client.Index<Post>(post);

Of course C# is smart enough to infer Post so

var status = client.Index(post);

is sufficient. This will index post to /[default index]/posts/12. The type name posts is automatically inferred from the type.

If you need more control, there are plenty of overloads, i.e:

 client.Index(post, i => i
    .Index(index)
    .Type(type)
    .Id(post.Id)
);

You can also construct the index request using the object initializer syntax instead:

var request = new IndexRequest<Post>
{
    Index = index,
    Type = type,
    Id = post.Id
};

client.Index<Post>(post);

var task = client.IndexAsync(post); // IndexAsync returns a Task<ConnectionStatus>