In order to access the parts of the web where you'll find darknet markets for weed, you need to start by downloading Tor, the most popular system for anonymous web browsing. Read all of their recommendations before installing, and be sure you've got the latest version. Use the Tor browser whenever accessing the Dark Web.
Know how you instinctively roll up the car windows when cruising into a bad neighborhood? Exploring the Dark Web is a lot like that. Many suggest that you get yourself some PGP encryption software, which will let you send your personal information in an encrypted format. GnuPGP is a solid option. Once you've downloaded it, learn how to get a personal key pair, as well as how to encrypt and decrypt text, on your specific operating system. Here are tutorials for Windows, OS X, and Linux. Encrypt everything! Some will recommend that you also cover your webcam with tape while browsing, as a precaution against hackers peaking back at you. Just pretend you're a spy and it'll be much more fun.
To buy anything dodgy on the Internet, exp. on darkweb, you'll need Bitcoins. They can be purchased at sites like LocalBitCoins. Reddit's /r/bitcoinmarkets is a useful resource for investigating your options and making sure you're using the best service you can. You'll probably want to tumble your coins so that they can't be traced back to you. Helix is a common option that works. It's worth your time to cover your tracks.
As you probably expect, navigating the Dark Web isn't as simple as getting around the Internet normally is. You may sympathize with your grandparents at first. With major marketplaces like The The Silk Road and several of its replacements being shut down by the Feds, finding a reputable place to purchase drugs can be a challenge. With this updated Hidden wiki 2022, you can find a lot of reputable drug markets on the darkweb. Tor has its own directory of sites you can browse as well. Some popular options like Agora require referral links, which can often be obtained on its forums. Be patient, but do your research to make sure you find a decent market that's not likely to scam you.