1) Go to https://bridge.xdaichain.com/. Connect your web3 wallet (MetaMask, Nifty Wallet) to the Ethereum Mainnet. Once connected, you will see your address populated in the header, and your DAI and xDai balance displayed on the page.
Note: If you change the dropdown on the page (ETH Mainnet) but not in MetaMask, the interface will shift but your wallet will not auto-connect to the chain. Switching chains in MM will automatically shift the interface.
2) Enter the amount of Dai you would like to transfer to xDai, and click the Transfer button.
3) The web3 wallet window will open with transaction details. Default gas price is fine, if you would like a faster transaction you can increase. Click Submit or Confirm (depending on wallet) to process the transaction.
4) Wait for the transaction confirmation (time depends on gas price and network throughput). The transaction is considered finalized after 8 blocks. To check on a pending transaction, click on the tx in the UI.
5) Once the initial transaction is successful, you will see consecutive Transfer Pending notifications with:
8 of 8 block confirmations.....
Countdown with continue until 1 block confirmation is left.
Waiting for execution on xDai Chain side.
6) Click on View on BlockScout to see details about the transaction. If you scroll down you will see the address (your address where the xdai was sent), value (amount sent in wei), and transactionHash, which will match the hash from the initial transaction.