Redmine

Hello all,
I tried to create a user using the http method post. it's not working. The page was /users.xml and /users.Json.
I use Postman which is an app for Google chrome browser. I used it to check if there is a "POST" method for the request but it's said there is no "POST" and there is only "GET" method that will get all users.

What should I do.
I am building an iOS app for redmine and I want my users to have the ability to register from the app.

Thank you.
Hind