Fixes #1218: Update acsf-setup.md with subprofile guidance.

readme/acsf-setup.md

@@ -3,9 +3,21 @@
 To configure a project to run on ACSF, perform the following steps after initially setting up BLT:
 
 1. Execute `blt acsf:init` from the project root.
-1. Create a custom module in `docroot/modules/custom` that will be used in lieu of a custom profile.
-1. Add `acsf` as a dependency for your custom module.
-1. If using lightning, create a custom [lightning.extend.yml](https://github.com/acquia/lightning/blob/8.x-1.x/lightning.extend.yml) and add it to `sites/default`
-1. Deploy to Cloud using `blt deploy`
+1. Create a custom profile:
+    - If you are using Lightning, create a custom sub-profile as described [here](https://docs.acquia.com/lightning/subprofile).
+    - For non-Lightning use cases, a profile can be generated [via Drupal Console](https://hechoendrupal.gitbooks.io/drupal-console/content/en/commands/generate-profile.html).
+1. Add `acsf` as a dependency for your profile.
+1. Modify the `profile` key under `project` in `blt/project.yml` to use the newly created custom profile. See example below with a profile named `mycustomprofile`:
+
+        project:
+          machine_name: blted8
+          prefix: BLT
+          human_name: 'BLTed 8'
+          profile:
+            name: mycustomprofile
+
+1. Deploy to Cloud using `blt deploy`. (Code can also be deployed via a [Continuous Integration setup](http://blt.readthedocs.io/en/stable/readme/deploy/#continuous-integration)
 1. Use ACSF's "update code" feature to push the artifact out to sites.
-1. When creating a new site, select "Lightning" as the profile.
+1. When creating a new site, select your custom profile as the profile.
+
+**Note:** The above process will not work for updating existing ACSF sites using lightning.