It basically is self explaining :
Enter a page name
Enter an external url
depending on theme display area add height and width ( in pixels f.e. 900 600).
Iff it fits > no scrollbars iff larger than scrollbars > yes (what you like)
userclass = who may see it.
it provides you after creation (on top of main plugin page) the url used.
copy this (norm. would display 2 url's ; just observe the paths; select 1) and create in navigation a page link (standalone; using parent etc...)
The external page (iff allowed from origin!!!) will display inside the iframe.
(works with latest version).