How do you import existing resource using Terraform import?

1. Identify which resource you want to import.
2. Write terraform code matching configuration of that resource.
3. Run terraform command terraform import RESOURCE ID

eg. Let's say you want to import an aws instance. Then you'll perform following:

1. Identify that aws instance in console
2. Refer to it's configuration and write Terraform code which will look something like:

resource "aws_instance" "tf_aws_instance" {
  ami           = data.aws_ami.ubuntu.id
  instance_type = "t3.micro"

  tags = {
    Name = "import-me"
  }
}

3. Run terraform command terraform import aws_instance.tf_aws_instance i-12345678