Technically, third party plugins are off-topic for this site.
However this is an easy one – in the Custom Fields page in the admin area, go into your field group. Scroll right down to the bottom and there’s a section allowing you to “hide” elements in the post.
Select the “content” option here and you’re done.
Keep in mind that if you have multiple field groups on the one post, you will need to hide the elements you want on the the first visible field group.