Add Page popup Content editor
Please see screen shot.
When you install concrete5 without sample content, there is one page type available called Page. Page includes a Content block in its Composer form.
To see what default blocks, properties, and attributes are set for the Page page type, navigate to the Page edit form.
Dashboard > Pages & Themes > Page Types > Page > Edit Form button
How do I go about using the content filled out in this area, in my code? I mean, I have an Area called Main but that block doesn't automatically get added. Do I need to do the same as with 5.6 and go to the page type defaults, and then add a block, and then make it Available to Composer (the area)? Sorry if this doesn't make sense...
This thread reply describes how to set the defaults for page templates: