Go to sushiswapclassic.org/staking - and unlock your wallet.
From there you'll be able to see the "Sushi Bar" where you can stake Sushi (turning it into xSushi) in order to earn part of the 0.05% trade fee from all pools on the exchange.
Step 3: First, you may need to "Approve" the Sushi token before you are able to use it. Simply hit the "Approve SUSHI" button and sign the transaction with your wallet or MetaMask.
Step 4: Once the Sushi token is approved you'll be able to hit "Convert to xSUSHI" to stake your Sushi.
Step 5: Then a new window prompt will pop-up letting you select how much SUSHI you want to stake. Select the amount, hit confirm and send the transaction.
Step 6: After that you will see the xSushi available in the bar.
The amount of xSUSHI in the SushiBar will not change. But the amount of Sushi it represents will. As fees are collected they are converted to $SUSHI and distributed proportionally across holders in the xSUSHI pool. So when you withdraw your xSUSHI back into $SUSHI it will be worth more $SUSHI than when you put in. These rewards are slower to update (because they cost a lot of gas) and so you should expect them to update, on average, once per day. Currently there is no way in the UI to see the level of rewards until you withdraw. The team is working to fix this.