Pages – rename manually?

I created a page, gave it a “slug” – I have some customization going on so the place where the menu might display it is not available. So, my page is currently located at https://www.mydomain.com/page_id=5.

Do I have to manually alter the .htaccess to have it display https://www.mydomain.com/pagename.html ? What would the rewrite rule be to change:

https://www.mydomain.com/page_id=5 to https://www.mydomain.com/pagename.html

I’m using version 2.1.3 and under options reading, I don’t see the page I’ve created.