Add README.md

Author: mootrichard

README.md

@@ -5,6 +5,7 @@ This quick start guide makes the following assumptions:
 - You are familiar with using AWS Lambda & AWS API Gateway, and have an [active AWS account](https://aws.amazon.com/).
 - You have a Square account enabled for payment processing. If you have not enabled payment processing on your account (or you are not sure), visit [squareup.com/activate](squareup.com/activate).
 - You are familiar with basic NodeJS development.
+- You have NodeJS installed on your local system.
 
 ## Before you start
 Clone this repo (if you have not already): [https://github.com/mootrichard/serverless-backend-quick-start](https://github.com/mootrichard/serverless-backend-quick-start)
@@ -20,4 +21,10 @@ If you haven't already created a function in AWS, you'll want to navigate to the
 
 You'll find a create function button in the top right that will allow you to create a new Lambda function. You'll be prompted through a wizard for configuring your function. The only required configuration for this quick start is using `Node.js 8.10`. You must also select an appropriate IAM profile to associate with your function.
 
-After completing the wizard, you'll have another editor that you can edit the function in. You'll want to select the drop-down titled "Code entry type" and select "Upload a .zip file". Click the "Upload" button that appears and upload the `chargeForCookies.zip` file. Click "Save" found at the top-right. You should now see your function in the AWS editor as it appears in your local editor.
+After completing the wizard, you'll have another editor that you can edit the function in. You'll want to select the drop-down titled "Code entry type" and select "Upload a .zip file". Click the "Upload" button that appears and upload the `chargeForCookies.zip` file. Click "Save" found at the top-right. You should now see your function in the AWS editor as it appears in your local editor.
+
+The final step here is to add 2 environment variables. One if for `ACCESS_TOKEN` which you add your OAuth `access_token` or your personal `access_token`. The other environment variable to add is `LOC_ID` which should be the location ID for which you're processing payments.
+
+## Step 4: Add AWS API Gateway as trigger
+
+Next, you'll want to click on AWS API Gateway under "Add triggers". This will allow you to create an HTTP endpoint to POST your `nonce` to in order to process payments.