I have set up a demo editor account and a sample page so you can experiment and play with the editor without doing any damage to existing pages - better to learn on a junk page first!
To enable you to do that, I've set up a demonstration user - please use it only to play, learn, and test - not for ongoing editing.
The user is: "demoeditor"
The password is "demopass".
Practice on this page (not the page you are reading at this moment).