So far, you have probably been using a browser to test your server. That works fine with simple GET requests (the kind of request a browser sends when you type a URL into the address bar), but it's not very useful for any other HTTP methods or requests with custom headers and bodies.
Servers are built to be used by clients. As you develop your code, you should be using a tool that makes sending one-off requests to your server easy! Here are some of my favorites:
Use whichever client you like, but make sure you're using one!