The Tor Browser
The Tor browser is a browser is the vehicle you use to access the dark web. However, your Internet Service Provider can detect when the browser being used. That is because Tor node IPs are public. There are two ways to combat this issue. You either need to use a Tor Bridge (a Tor node that is not public indexed) or use a VPN. For those that are in the US, connecting to a VPN is a more reliable option. Since your ISP can sell your data and browsing habits, they can easily tell if you are using the Tor browser.
Dark Net vs Deep Web
Though you have probably heard the terms used interchangeably, there is a big difference. The deep web is simply all of the information stored online that is not indexed by search engines. If you still want to access info that is no longer indexed, you need a specialized search engine. That said, there are very few of them that even still work. The two that are still usable are www.surfwax.com and the original index of the web, vlib.org. Keep in mind though that they may not do as good of a job as others.
The Dark Net or Dark Web is kept hidden on purpose. That is because it usually deals with illicit markets. Usually, you need a special tool to access the content there. The advantage of using the dark web is anonymity. It is often used by whistleblowers and journalists to exchange sensitive information.
Access the Dark Web Safely
There are a few things that you should know. The Tor Browser is based on the Firefox browser. Also, most of the endings of the dark web sites end in .onion instead of .com. When you use it, it tells the browser to access the dark web through the onion router. There are a handful of sites that do an index on onion sites. Those include Onion.city, Onion.to, and NotEvil. Again, be extremely cautious if you decide to access the deep web/darknet. You now see how to access it. However, be sure to use a VPN whenever you engage in that sort of activity.