How to make login React.js & Spring application

I really need some help! I need to do web app with react.js in front-end and spring as back-end. Now I am trying to make login using Jwt. But it is just not working.When I am trying to access post method in browser it just saying that request GET is not supported. No react.js is showing, no errors in console. Also it is pretty hard for me to find some examples with react and spring on internet. Maybe someone have ideas or examples how I can do it.? Not necessarily just I need quit simple but working login/logout. Thanks.

Also this is my project as I have it now: https://github.com/DonneGri/HealthProject