Let's run over each of the steps again. Most of them are similar to Ethereum version. However, you will need to add BSC network into your wallet, and you will need to find a bridge that suits you best.
Unstake & Withdraw
Go to Rewards page
Go to Pool 1
Press Max, then Unstake
Go to Deposit – Find Withdraw button on the bottom
Select Max to withdraw in balanced proportion,
(Optionally) Press stablecoin logo to withdraw all in this stablecoin
Press Withdraw and sign the transaction
Also, keep in mind that xSigma BSC operated their pool with USDC, USDT and BUSD. This means you wouldn't need your DAI, and you either need to convert them to BUSD, or don't withdraw SIG-LP to DAI to begin with.
Find any bridge than allows ETH-BSC crosschain movement. Many CEX support output funds into BSC blockchain, including Binance.com. There also exists Anyswap.exchange as a more decentralized solution.
! Disclaimer ! Anyswap is not affiliated with xSigma. We only use this as an example. We recommend doing your own due diligence and selecting the most convenient and secure bridge option for you.