Step one — installing the Tor Browser
The first step is a clean install of the Tor Browser. The Tor Browser is a tuned build of Firefox plus a Tor client, distributed by the Tor Project. It connects to the Tor network on launch and routes the pages you visit through three relays before they reach the destination.
Downloading the installer
The official source is the Tor Project website. Open it in whichever browser you already use, pick the version for your operating system, and save the installer to a folder you control. On Windows it is an .exe, on macOS a .dmg, on Linux a tarball you extract anywhere you like. If you are technically comfortable, verify the signature of the download against the published one — the project explains how on the same page. Most readers can skip the signature check on a first install and add it to the routine later.
Running the install
On Windows and macOS the installer behaves like any other; double click, follow the prompts and let it finish. On Linux extract the tarball to a folder and run the start-tor-browser script inside. The first launch asks whether to connect directly or via a bridge. Direct is the right answer unless your network filters Tor, which most home networks do not. Click connect, wait a few seconds for the network connection to come up, and the homepage of the Tor Browser appears.
Setting the security slider to Safest
Open the shield icon in the toolbar and pick Safest. That setting disables JavaScript on non-HTTPS pages, blocks several font and media features that are common fingerprinting surfaces, and trims the attack area to roughly what the storefront actually needs. Mars Market is built and tested against the Safest setting, so nothing on the storefront breaks. Other clearnet pages may look duller at this level, which is the price of being unremarkable.
Confirming a working install
Visit the page the Tor Browser shows at first launch — it confirms that the connection is routed through Tor. If the page reports a successful Tor connection, the install is done. Close the browser when you are ready to move on. The next step copies a verified Mars Market mirror, and the page you reach there does not work in any other browser, so leave the Tor Browser closed for now and open the next step page in your regular browser.