The Tor Browser is the only way to open a darknet market, and the install is where most problems start, because the two mistakes that matter both happen before the browser ever opens. Here is the clean path and the two traps to avoid.
Where to get it
Download the Tor Browser from the Tor Project's own website. That is the only source that matters. The Tor Project publishes installers for Windows, macOS and Linux on a single page, and you pick the one that matches your machine. The check is the address bar. It should show the Tor Project domain. If you got there through a search result, a forum link, or a message that said to download it from a certain page, verify the domain before you run the installer, because typosquats around that domain have hosted backdoored installers before. A backdoored installer is a program that looks like the real one and does something else in the background, and the only defense is checking where it actually came from.
The two mistakes
The first mistake is installing a modified build. Some distributions and some "enhanced" packages ship a version of the browser with extra features bolted on, and those extras are exactly the kind of thing that breaks the isolation the browser is meant to provide. Use the stock build from the Tor Project, with nothing added. The second mistake is running it as an administrator or root out of habit. The browser is designed to run as a normal user, and elevating it gives anything it touches more power than it needs. Install it, run it as yourself, and leave the elevation for programs that actually require it.
First launch
The first time you open the browser it shows a Connect button. Click it and wait ten to thirty seconds while it builds a connection through the relay chain. When the home screen appears, you are routed through Tor. From there the security slider in the shield icon is the setting that matters most. Leave it on Standard for general browsing and move it to Safer when you are on a market, which turns off scripting and a handful of features that have been used in fingerprinting. Most markets, including Awazon, run fine on Safer, so there is no reason to relax it. The install is five minutes. The habits you build in those five minutes are what protect you for the next five years.