On the top of the page, next to the page's title, you should see an arrow button next to the Edit button. Press the arrow button to see the list of functions, and click on the function that says Classic Editor. It should take you to the editing page.
When editing a page, I would suggest looking at another editing page similar to the page you are editing on to serve as a guideline.
If you make any mistakes, don't worry; we'll fix it up. We all start from somewhere. Any more questions or concerns, just contact me or any other available administrator.