How can i change name of a btn after login in react?

Hi i am working on my new website.. I want to change the name of the Button shown below forms sign in to profile and on-click i want to show a side bar about that profile in react.

Note: This sign in button is on my NavBar.

    <NavBtn>
        <NavBtnLink to="/login">Sign In</NavBtnLink>
    </NavBtn>