Provider not defined (picture) ==> console output

For some reason I can't manage it to get a simple Signature prompt for my Ethereum based site. I have a button on the site that should open the signature prompt when clicked on it. I watched this youtube video: https://www.youtube.com/watch?v=wBr_N7CtIts

Copied everything what he wrote but for some reason I got the output "provider not defined" (he doesn't and i got the exact same code: )

const simpleSignature = async () => {
   const signer = provider.getSigner();
   let message = "Please verify you are the owner of the wallet";
   let signature = await signer.signMessage(message);

   let address = ethers.utils.verifyMessage(message, signature);

   console.log(address);
   console.log(accounts[0]);
   
}

   const signer = provider.getSigner();

This seems to be the badguy, can anyone help me solve this issue? Im totally new to JS and trying to figure it out, but with no success .