See https://cloud.google.com/sdk/docs/quickstart.
See https://www.terraform.io/downloads.html.
Go to https://console.cloud.google.com/identity/serviceaccounts and create a service account. And a JSON key for it.
Download the key file as ./infrastructure/service-account-credentials.json
.
Copy ./infrastructure/terraform.tfvars.example
as ./infrastructure/terraform.tfvars
. Replace the values as needed.
cp ./infrastructure/terraform.tfvars.example ./infrastructure/terraform.tfvars