The New York Public Library is a great resource, and you can get a card for free, no matter what borough you live in.
The NYPL offers many free classes, including those to do with computers, software, and using the internet.
You can also get help right here at the Hostos Library.
When you enter the library, come downstairs. Turn left into the room with computers. At the desk, you'll usually see two people: one person is a librarian, and the other is a tech tutor.
The Goodwill Community Foundation has this set of tutorials on a range of subjects about the internet that you may find helpful.
The BBC (British Broadcasting Corporation) has this webpage with useful links about basic internet concepts and skills. (Most of their information is true no matter where you live, but you'll notice a few things they mention that are specific to Great Britain.)