There are many sources of digital books; there are three just through the LA County library system. The digital approach I know best is OverDrive through the LA County library, so I'll briefly describe that one.
To use the LA County library system, you need a library card for that system and you need to know your card PIN. For the LA County system, good news: If you don’t have a card, you can be issued an Instant Digital Card! Isn’t that cool? If you have a regular card but can’t remember your PIN, I’d suggest you just get an Instant Digital Card now and sort out the duplication when regular library service resumes. You can also request a new PIN, although I'm not sure if that's automated or subject to staff availability: Get a PIN.
To search for digital materials, go to the library site and hover over the tab for Digital Library. Then click on either ebooks or audiobooks.
If you want to read on a device like a phone or iPad, you’ll need to download the corresponding app. I don't think you can download apps on iPads borrowed from school. For myself, I use my computer and choose read “on [my] browser.”
Not all books are in the public library's digital collections but many are. You might think digital copies would be unlimited in number, but that is not the case. A branch has access to certain titles and a limited number of copies, just like physical books. You can always hold a digital copy like you would a physical copy, and you’ll get an email when it’s available.
If you have any questions, just email me. If I don’t know the answer right away, I’ll find out! Most important: give it a try. It’s really pretty logical to set up--and besides, figuring out how to do something new sounds rather like at-home learning in and of itself.