Comment on Massive Passive Profits Plugin Setting Up a Sub-Domain Blog Template with Talian 05 by SEO Dave.
The non-multisite version of WordPress has it’s theme editor under “Appearance >> Editor” on every page of the WordPress Dashboard, since you are using Massive Passive Profits plugin you’ll be using WordPress multisite and it’s different, only Super Admins (that’s you) under the Network Admin section of the site can edit the themes.
To access the theme editor on a multisite installation:
On the top right click the “Howdy Admin” arrow, followed by “Network Admin”.
On the left menu under “Appearance” click “Editor”.
Don’t know about using the Massive Passive Profits plugin to post articles, I don’t use the plugin on my sites. I understand there was an update to the plugin, maybe that fixed the issue (I’m guessing)?