You can swap and bridge DAI to xDAI from the funding tab on bookmaker.XYZ.
Head to the funding tab on bookmaker.XYZ
On the tile that says "I have crypto" select "Transfer Now".
If you have DAI on a source chain and you have the network selected, XYZ will recognize this and take you straight to bridging.
If this is the first time you're interacting with Hop via bookmaker.XYZ. You will need to approve the contract interaction. Select "Approve" and confirm the TX in your wallet.
Once the contract approval has confirmed, select "Bridge" and confirm the TX in your wallet.
Wait for the bridging process to complete. The time differs depending on the source chain.
Once it has confirmed on chain, you have successfully bridged DAI from your source chain to Gnosis Chain xDAI. You can begin placing bets.