Hi @Suzana_Maranhao,
You can use the GSN Starter Kit to start.
Then deploy the Counter contract to Rinkeby using the following instructions:
Then in App.js
change the web3 context to useWeb3Injected
with GSN true (commenting out any other context). (as per: Sign GSN relayed call with MetaMask)
const context = useWeb3Injected({gsn: true});
Change MetaMask to use Rinkeby network.
You can then press Increase Counter/Decrease Counter and the user will get a Signature Request from MetaMask to sign, and once signed the GSN will relay the call.
Feel free to ask all the questions that you need.