Automate Web Login process

This is my first question, so sorry if I ask the wrong thing at the wrong place.

I am implementing an automated log in in a web page. My client is a C# application that displays a browser in a window Form, with the typical Login Username, Password and Login button If the user types the correct information, you get access to the REST api’s

I want to implement an automated log in so we can automate some testing. I have the user and password stored in Windows Credentials

How can I automate the typing of the user and password and the click the login button without user intervention?

I have no experience using JavaScript and could not find a way to do this

A generic answer with some C# code to investigate will be helpful as well

I found answers using Testing packages, but I just need a simple solution to automate the login

Thanks