How to API Create..?

[Authorize] is used for security like if you pass token with your request then its work

Below is sample link for creating WebAPI in MVC

https://atozsourcecode.com/BlogPost/Index/cffb4057-1a07-4f81-bd88-35b7c2c8c295/how-to-create-simple-web-api-step-by-step-and-how-to-call-api-from-browser

I hope above link is help you

We can use [FromBody] for Post Method of API and when we want to pass json that time it is use
If you want to create Role Based Api then use Authorise.

[Authorise(Role="Admin")]
[HttpPost]
public HttpResponseMessage Index([FromBody] IndexViewModel)
{
return Ok(); 
}