Rails how to Use mail_form? [duplicate]

This question already has answers here: Contact Us form in Rails 3 开发者_如何学运维 (3 answers) Contact us functionality in Rails 3 (4 answers) Closed 2 years ago.

I'm trying to use mail_form under Rails for a contact us form on a page.

But the instructions are rather confusing, does anyone know of a tutorial or how to use it?

Step by step pls. Thanks in advance!