How to display the username in the admin section, based on the login user who enters the system (ReactJS)

I have a login form that contains email and password, how do I get the username from the login used and displayed in the “Admin” sidebar and will be the name of the logged in user

here’s the image : (https://i.stack.imgur.com/zE7t3.png)

btw, I cant post the image, because it says “You need at least 10 reputation to post images.”