For the first time ever, Apple will stream the event live on YouTube.
Apple Event 2019: How To Watch, Live Stream

Otherwise, Apple will host a livestream of the event on its Apple Events page. If you are an Apple TV owner, you can also watch the livestream via the Apple Events app - there are also archives of older events if you're feeling nostalgic.

Today, on Sept. 10, Apple will hold its annual fall event where it will likely announce the iPhone 11 along with other products and services. The event begins at 10 a.m. PT at the Steve Jobs Theater on Apple's campus in Cupertino, California. Apple is expected to announce three new phone models, replacing the iPhone XS, XS Max and XR with the rumored iPhone 11, 11 Max/11 Pro and 11R. The phones will likely add improved cameras, faster processors and iOS 13. We also expect to see an Apple Watch update. However, whether this is a brand new Apple Watch 5 or a more minor Apple Watch upgrade remains to be seen.