You can start testing xDai on Cargo by going to https://rinkeby.cargo.build. In order to get up and running you will need to complete the following steps:
Use MetaMask to sign up on the Cargo test site.
Add the xDai testing network to MetaMask.
Fund your wallet using the test xDai faucet.
MetaMask will be required to test xDai on the Cargo test site. After you've installed MetaMask in your browser go to https://rinkeby.cargo.build and either sign up with a new account which is linked to your MetaMask wallet, or sign in with an existing account. You should be connected to the Rinkeby network prior to signing up.
We will use the Sokol test network for this. Click on the network dropdown in MetaMask (see above screenshot) and choose "Custom RPC"
Fill in the Sokol Network Details and click Save. Sokol will now be available in the dropdown list.
Network Name: Sokol Testnet
New RPC URL: https://sokol.poa.network
Block Explorer URL: https://blockscout.com/poa/sokol
Connect to the Sokol test net in MetaMask and go to the faucet website - https://blockscout.com/poa/sokol/faucet
Enter the address that you'd like to test with and request test funds.
Now you are ready to test xDai functionality on Cargo! You can connect to the Sokol test network and deploy xDai smart contracts on Cargo.