You'll find this at the bottom of the screen on an iPhone, or at the top on an iPad. This will display all of the bookmarks you have saved. This will allow you to remove items from the list. If the bookmark you want to delete is in a folder, open the folder first and then tap "Edit." Tap "Delete" to confirm. You cannot delete the Favorites or History folders, but you can delete items inside of them.

Summary:
Tap the Bookmarks button. Tap the Bookmarks tab. Tap the "Edit" button. Tap the "-" next to the bookmark or folder you want to remove.