How do I delete synced picture albums off the iPhone?

I selected sync to get pics from my phone to my computer not realizing all my pics from my computer would go to my phone. I now have over 4000 pics in dozens of albums from my genealogy research on my phone. How do I delete them?

To delete synced photos and videos from your device

1. In iTunes, click the Device button in the upper right corner. (If viewing the iTunes Store, click the Library button in the upper-right corner first.)
2. Click the Photos tab in the resulting window.
3. Choose "Selected albums" and deselect the albums or collections you want to delete.
   Note: To delete all synced photos, deselect "Sync Photos from" and, when asked, click "Remove photos."
4. Click Apply.

Source: iTunes: Syncing photos - Apple Support

The only thing in the right corner is a square that says playlist with a magnifying glass.

There is no button that says library.