The whole job is four steps: install the browser, load a mirror, verify the address, log in. Each step has one failure mode, and knowing it in advance saves you the hour you would otherwise spend wondering what went wrong.
Install the browser
Go to torproject.org and type the address into your current browser. Do not click a search result for the download page, because sponsored copies of that page exist and they add software to the installer. Download the build for your operating system, install it, and open it. The first window you see is a welcome screen with a connection indicator. Leave it there for a few seconds until the circuit builds. If it stays red, your network is blocking Tor, and the bridge option in the settings is the fix. Most people never need it.
Load a mirror
Copy one of the addresses from the mirror list. Paste it into the address bar and press Enter. Expect 20 to 40 seconds on the first load, because the browser is building a fresh route through three relays. The page will look plain while it settles. If the address does not resolve at all, wait a minute, reload once, then try the next mirror. That is normal rotation, not a broken setup.
Verify before you log in
Read the address in the bar and compare it with the one you copied, character by character, from the end backwards. Clones differ by one or two characters and are easiest to catch at the tail of the string. This takes five seconds. It is the single most effective anti-phishing habit on the dark web, and it is the one people skip most.
Register and lock the account
Create the account with a username that has nothing to do with your name, your handle from other places, or your email. Choose a long password, something you have never used. After the first login, open the security settings and enable two-factor authentication. Generate a PGP key in the same settings screen if you do not have one, because you will need it for vendor messages.
What goes wrong
The three failures that actually happen are: the wrong download source, a mistyped address, and logging in before checking the address. The first two you catch by typing the URL yourself and copying instead of typing. The third you catch with the backwards comparison. Everything else, a slow load, a blank page, a warning banner, is either congestion or a cosmetic setting, and it resolves by waiting and reloading.
For the security settings that matter once you are in, see Tor Browser security settings. For what the market is and what it costs, see the market overview.