Add pre-requisites section to README

This section talks about creating the AWS test user and the repository
secrets it requires.

Author: jsf9k

README.md

@@ -15,6 +15,52 @@ Actions](https://github.com/features/actions) configurations
 appropriate for an Ansible role, as well as the Terraform code to
 create the AWS test user.
 
+## Pre-requisites ##
+
+In order to execute the Molecule tests for this Ansible role in GitHub
+Actions, a build user must exist in AWS. The accompanying Terraform
+code will create the user with the appropriate name and
+permissions. This only needs to be run once per project, per AWS
+account. This user can also be used to run the Molecule tests on your
+local machine.
+
+Before the build user can be created, the following profile must exist in
+your AWS credentials file:
+
+* `cool-terraform-backend`
+
+The easiest way to set up that profile is to use our
+[`aws-profile-sync`](https://github.com/cisagov/aws-profile-sync)
+utility. Follow the usage instructions in that repository before
+continuing with the next steps. Note that you will need to know where
+your team stores their remote profile data in order to use
+[`aws-profile-sync`](https://github.com/cisagov/aws-profile-sync).
+
+To create the build user, follow these instructions:
+
+```console
+cd terraform
+terraform init --upgrade=true
+terraform apply
+```
+
+Once the user is created you will need to update the [repository's
+secrets](https://help.github.com/en/actions/configuring-and-managing-workflows/creating-and-storing-encrypted-secrets)
+with the new encrypted environment variables. This should be done
+using the
+[`terraform-to-secrets`](https://github.com/cisagov/development-guide/tree/develop/project_setup#terraform-iam-credentials-to-github-secrets-)
+tool available in the [development
+guide](https://github.com/cisagov/development-guide). Instructions for
+how to use this tool can be found in the ["Terraform IAM Credentials
+to GitHub Secrets"
+section](https://github.com/cisagov/development-guide/tree/develop/project_setup#terraform-iam-credentials-to-github-secrets-).
+of the Project Setup README.
+
+If you have appropriate permissions for the repository you can view
+existing secrets on the [appropriate
+page](https://github.com/cisagov/skeleton-packer/settings/secrets) in
+the repository's settings.
+
 ## Requirements ##
 
 None.