After breakfast you can grab a cab or head back to the subway at High Street - Brooklyn Heights to catch the A or C train or the 4 or 5 train from Borough Hall. Either way you’ll need to get to the Battery Park Ferry Station to catch the ferries to Ellis Island and the Statute of Liberty. There is a ton of information available on the National Parks Service site about visiting Ellis Island. Linked above and here: https://www.nps.gov/elis/planyourvisit/index.htm While there is no fee to enter Ellis Island or the Statue of Liberty the islands are only accessible via ferries and tickets are required to board the ferries. You can checkout the Statute Cruises site here: https://www.statuecruises.com