update README

Author: davidbloss

README.md

@@ -22,6 +22,14 @@ be defined to uniquely customize each account.
 
 ## Updating An OpsLevel Account
 
+First, **ensure OPSLEVEL_API_TOKEN is set** via `export OPSLEVEL_API_TOKEN=<YOUR_API_TOKEN>` - this is how Terraform knows which account to update!
+
 For a preview of planned changes,run `task plan`. No changes will be made with this command.
 
 To apply changes, run `task apply`. This will refresh Terraform's state then prompt you for approval to apply changes.
+
+> IMPORTANT: Managed resources/data are stored in Terraform's state, which is this local file `workspace/terraform.tfstate`. If this is lost, Terraform will not be able to properly apply changes.
+
+### OpsLevel account Clean up
+
+To remove all Terraform managed data, run `task destroy`. Terraform will prompt you for approval before deleting all managed resources.