Update README.md

Added usage instructions for the yugabyte terraform AWS module.

README.md

@@ -1,2 +1,78 @@
 # terraform-aws-yugabyte
 A Terraform module to deploy and run YugaByte on AWS.
+
+## Config
+
+```
+module "yugabyte-db-cluster" {
+  source = "./terraform-aws-yugabyte"
+
+  # The name of the cluster to be created.
+  cluster_name = "tf-test"
+
+  # A custom security group to be passed so that we can connect to the nodes.
+  custom_security_group_id="SECURITY_GROUP_HERE"
+
+  # AWS key pair.
+  ssh_keypair = "SSH_KEYPAIR_HERE"
+  ssh_key_path = "SSH_KEY_PATH_HERE"
+
+  # The vpc and subnet ids where the nodes should be spawned.
+  vpc_id = "VPC_ID_HERE"
+  subnet_ids = ["SUBNET_ID_HERE"]
+
+  # Replication factor.
+  replication_factor = "3"
+
+  # The number of nodes in the cluster, this cannot be lower than the replication factor.
+  num_instances = "3"
+}
+```
+
+**NOTE:** If you do not have a custom security group, you would need to remove the `${var.custom_security_group_id}` variable in `main.tf`, so that the `aws_instance` looks as follows:
+
+```
+resource "aws_instance" "yugabyte_nodes" {
+  count                       = "${var.num_instances}"
+  ...
+  vpc_security_group_ids      = [
+    "${aws_security_group.yugabyte.id}",
+    "${aws_security_group.yugabyte_intra.id}",
+    "${var.custom_security_group_id}"
+  ]
+
+```
+
+## Usage
+
+Init terraform first if you have not already done so.
+
+```
+$ terraform init
+```
+
+Now run the following to create the instances and bring up the cluster.
+
+```
+$ terraform apply
+```
+
+Once the cluster is created, you can go to the URL `http://<node ip or dns name>:7000` to view the UI. You can find the node's ip or dns by running the following:
+
+```
+terraform state show aws_instance.yugabyte_nodes[0]
+```
+
+You can access the cluster UI by going to any of the following URLs.
+
+You can check the state of the nodes at any point by running the following command.
+
+```
+$ terraform show
+```
+
+To destroy what we just created, you can run the following command.
+
+```
+$ terraform destroy
+```