WordPress editor question.

I find this very strange. I posted this question a little less than two hours ago. When I went to see if there were any postings, it has disappeared from the list. I am submitting it again.

Trying to install a new page or a new post I get to the Yoast editor instead of the WordPress WYSIWYG editor. How can I switch back and forth from one editor to the other?

Thank you very much in advance for your help and advice.