From nothing to the storefront in four steps.
Reaching Nexus takes four steps, and doing them in order closes most of the ways a first visit goes wrong.
Download Tor Browser only from the official Tor Project site, verify the signature on the first install, and set the security level to Safest. A normal browser cannot open an onion address, and Safest closes the biggest hole by turning scripting off. Nexus works fine at Safest.
Copy an address from the verified list on this page, never type a fifty-six character string by hand. Open it in Tor Browser. When the login loads, hold the address in your bar against the one the captcha prints. Match means genuine, mismatch means close the tab. Then register with a fresh username and a unique password.
Nexus Market