Gettings Started With Multiple Windows

I would like to open a window containing some content on open and press a button to close this window and open a different one. I have tried using the Resizeable window class but to no success. I just get assertions from the window having no size or from incorrectly setting the content. Could somebody guide me on how to use Windows?

Sorry for the noob post!

study the Demo Project’s “Window” demo.