how to deploy on sepolia testnet instead of hardhat localhost?

[elvisisvan]

i'm trying to deploy my contract on ethereum sepolia network but encountered this error:

Error: sending a transaction requires a signer (operation="sendTransaction", code=UNSUPPORTED_OPERATION, version=contracts/5.7.0)

i have added const signer = provider.getSigner(); according to this answer on stackoverflow but the error is still there, here's my App.js code:

...
  const loadBlockchainData = async () => {
try {
      const provider = new ethers.providers.Web3Provider(window.ethereum)
      setProvider(provider)
      const signer = provider.getSigner();
      const network = await provider.getNetwork()
      const chainId = network.chainId;
      const contractAddresses = config[chainId];
      if(!contractAddresses) {
        throw new Error(`No contract deployed to chain with id ${chainId}`);
      }
  
      const carbonCredit = new ethers.Contract(config[network.chainId].carbonCredit.address, CarbonCredit, provider)
      const totalSupply = await carbonCredit.totalSupply()
      const credits = []
  
      for (var i = 1; i <= totalSupply; i++) {
        const uri = await carbonCredit.tokenURI(i)
        const response = await fetch(uri)
        const metadata = await response.json()
        credits.push(metadata)
      }
  
      setCredits(credits)
  
      const escrow = new ethers.Contract(config[network.chainId].escrow.address, Escrow, provider)
      setEscrow(escrow)
  
      window.ethereum.on('accountsChanged', async () => {
        const accounts = await window.ethereum.request({ method: 'eth_requestAccounts' });
        const account = ethers.utils.getAddress(accounts[0])
        setAccount(account);
      })
} catch (error) {
  console.error("Error loading blockchain data", error);
}
  }

  useEffect(() => {
    loadBlockchainData()
  }, [])
...

can anyone help me with this? i'm more than happy to provide more related code if you ask, any help would be awesome