Step 1: Update your farmer node to at least Chia 1.2 and sync with the network.
Step 2: Receive some XCH (you can get some from the faucet).
Step 3: Create Plot NFT. Once you have some XCH in your wallet, go to the pool tab, and click on "Add a Plot NFT". Select "Connect to pool" and enter https://pool.21chia.com
Step 4: Create plots for the NFT ("Add plot" in the ... menu for the NFT). We recommend using the MadMax plotter instead, though. You'll need your farmer public key (parameter -f) and your pool contract address (parameter -c).
Changing Pool: if you are already on another pool and want to change to 21Chia, click on the "Change pool" button in your NFT and enter our URL when asked: https://pool.21chia.com On the CLI, you can change pool with chia plotnft -i 2 -u https://pool.21chia.com When you change pool, your plots linked to the NFT will switch to farming on the new pool.