update

vpc-transit-gateway-association/README.md

@@ -101,6 +101,9 @@ The `route_prefix_list_name` allows you to select a route shared prefix (automat
 simplicity of routing setup to direct traffic through the TGW (vs using 0.0.0.0/0, the default route).  A future feature
 will allow the use of the default route and add the use of a VPN prefix list.
 
+You must also add `twg_environment` to the `variables.vpc.auto.tfvars` file so you can place the VPC into one of the six
+available enviroments: services (for common, shared), dev, test (for test, UAT, QA, ITE), stage, prod, and cre.
+
 ```hcl
 module "vpc_tgw_data" {
   source = "git@github.e.it.census.gov:terraform-modules/aws-vpc-setup.git//vpc-transit-gateway-association/data?ref=tf-upgrade"