Nexus Market lives on the Tor network, which means the only way to open it is through Tor Browser. This guide walks through the whole path: installing the browser, opening a mirror, setting the security level, and verifying the address before you type your password. If you already use Tor Browser, skip to the section on mirrors.
Install Tor Browser
Go to torproject.org and type the address yourself. Do not click a search result for the download page, because ad-funded copies exist and they bundle extra software into the installer. Download the version for your system, install it, and open it. The first launch builds a circuit, so give it a few seconds before you judge the connection.
Two settings matter. Leave the security level on Standard for normal browsing, and move it to Safest when you are logging in or paying. Safest disables some web features in exchange for a stronger circuit, which is worth it at the moments that actually expose you. The other setting is the bridge option, which you only need if your network blocks Tor. Most users never touch it.
Open a Nexus Market mirror
Copy one of the addresses from the mirror list and paste it into the address bar. Press Enter and wait. The first load takes 20 to 40 seconds while the circuit forms, and the page may look plain at first. When it settles, you should see the market's interface. If the address does not resolve at all, wait a minute, reload once, and try the next mirror.
Verify before you log in
Once the page has loaded, read the address in the bar and compare it character by character with the one you copied. This is the single most effective anti-phishing step on the dark web, and it takes five seconds. A clone gets your password once and is done with you. After that, log in, and if you are registering a new account, enable two-factor authentication in the settings immediately.
Day to day
Bookmark the mirror that loads fastest for you. Keep this site bookmarked too, because it is where the mirror list gets updated. When the market rotates addresses, the old ones stop resolving and the new ones appear here. Between rotations, nothing changes: same account, same balance, same orders, regardless of which mirror you use. If you registered a new account, the next step is the PGP key, because vendor messages and delivery details run through it. The PGP guide walks through generating the key and the first encrypted message.
For what the market is, what it sells and what it charges, see the overview. For how to tell a real .onion address from a cloned one, see onion links.