Hi@akhtar,
To ssh in your EC2 instance, you have to provide user and private key. In Terraform you can use connection keyword to ssh in EC2 instance. I have attached one example for your reference.
 connection {
    type     = "ssh"
    user     = "ec2-user"
    private_key = file("C:/Users/Nadeem Akhtar/Downloads/mysecure.pem")
    host     = aws_instance.web.public_ip
  }