Hi Melanie, I’m afraid that’s incorrect.
Have you checked out Ed’s Knowledge base under Flexform/Portfolio URL Rewrite?
It’s quite easy to do, but a couple of things to remember. Attached are the settings that I successfully use changing /includes/custom-post-types/portfolio-type.php
1) Line 48…a different recommendation to Ed. This includes a custom slug to replace portfolio. It’s important to choose a slug that is not used anywhere else. I have a page called “Video” (my portfilio page) so I had to use ‘videos’ as the slug.
2) Once done, make sure you go to settings/permalinks and save (no need to change settings from ‘post name’). This avoids the 404 error that you will get otherwise.
3) This will most likely need to be done each time you update the theme.
Cheers