Updated README.

README.md

@@ -1 +1,27 @@
-# terraform-aws-ami-showcase
+# terraform-aws-ami-showcase
+
+Data only Terraform module which describes generally used public AMIs.
+
+## Usage
+
+```hcl-terraform
+module "ami" {
+  source = "yukihira1992/ami-showcase/aws"
+}
+
+output "amazon_linux_ami" {
+  value = module.ami.latest_amazon_linux_image_id
+}
+
+output "amazon_linux2_ami" {
+  value = module.ami.latest_amazon_linux2_image_id
+}
+
+output "ecs_optimized_amazon_linux_ami" {
+  value = module.ami.latest_ecs_optimized_amazon_linux_image_id
+}
+
+output "ecs_optimized_amazon_linux2_ami" {
+  value = module.ami.latest_ecs_optimized_amazon_linux2_image_id
+}
+```