Among your import options is the option to scrape URLs from a page. Type a URL here and it'll place all URLs from that page into your "bulk addition" box except:
Relative URLs.
Internal links (URLs which contain the domain name of the page being scraped), if you check the box saying to exclude them.
If you've selected to not allow people to submit duplicates, all duplicates (URLs which area already in your directory) will be excluded.
You'll be able to review the list and remove those you don't actually want to add.