From what you described, it sounds like you’d like to display inside a tab (on the front-side of the site) the admin page to create a new church user. Is that correct? That would be much harder to do, compared to displaying existing page content.
1) The nicest way would be to have a frontend form which can create a new post (of the post type church_user). However, this plugin doesn’t have that function – I’m working on another plugin for creating input forms like this, but it’s not finished.
2) An alternative is just to have a link that goes to the admin page. For example:
<a href="[url admin]/post-new.php?post_type=church_user">
Click here to create a new church user
</a>
The user will have to log in, or already be logged in.
3) Another idea I have is probably not practical – to embed the admin page in an iframe:
<iframe src="[url admin]/post-new.php?post_type=church_user" width="100%" height="400px"></iframe>
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There’s a donation link in the plugin reference (Settings -> Custom Content) at the bottom of the page; or here in the right column under “Author”.
However, it would be nice to find a good solution for you first. ??