Add content to your website without having to do it manually

Hello I'm working on a project for a website.

Now what the project includes is that a person can offer his service through a form on the website which he submits after filling it out. An admin should get a message through mail or something else In which he can approve or deny the request.
If he approves the requester's service it should automatically be added to the website with the information given in the form in a pre chosen way.

Now my question Is how is it done?