diff --git a/.github/workflows/public-repos-scala-steward.yml b/.github/workflows/public-repos-scala-steward.yml
index d69e0ca..3a4774e 100644
--- a/.github/workflows/public-repos-scala-steward.yml
+++ b/.github/workflows/public-repos-scala-steward.yml
@@ -11,5 +11,6 @@ jobs:
     uses: ./.github/workflows/reusable-scala-steward.yml
     with:
       app_id: 214238
+      app_installation_id: 26822732
     secrets:
       private_key: ${{ secrets.SCALA_STEWARD_APP_PRIVATE_KEY }}
diff --git a/.github/workflows/reusable-scala-steward.yml b/.github/workflows/reusable-scala-steward.yml
index bfc37df..36982de 100644
--- a/.github/workflows/reusable-scala-steward.yml
+++ b/.github/workflows/reusable-scala-steward.yml
@@ -6,6 +6,9 @@ on:
       app_id:
         required: true
         type: string
+      app_installation_id:
+        required: true
+        type: string
     secrets:
       private_key:
         required: true
@@ -22,19 +25,13 @@ jobs:
         with:
           repository: guardian/scala-steward-public-repos
           path: common-config
-      - name: Generate token
-        id: generate-token
-        uses: tibdex/github-app-token@v1
-        with:
-          app_id: ${{ inputs.app_id }}
-          private_key: ${{ secrets.private_key }}
 
       - name: Execute Scala Steward
         uses: scala-steward-org/scala-steward-action@v2.54.0
 
         with:
-          # Use the token generated by the previous step and the 
-          # Guardian Scala Steward GitHub App
-          github-token: ${{ steps.generate-token.outputs.token }}
-          repos-file: REPOSITORIES.md
+          github-app-id: ${{ inputs.app_id }}
+          github-app-installation-id: ${{ inputs.app_installation_id }}
+          github-app-key: ${{ secrets.private_key }}
+          repos-file: REPOSITORIES.md # possibly no longer necessary, thanks to `github-app-*` configuration
           repo-config: common-config/scala-steward.conf # from checkout of guardian/scala-steward-public-repos
diff --git a/README.md b/README.md
index 21c3709..d64444c 100644
--- a/README.md
+++ b/README.md
@@ -8,8 +8,14 @@ instead!_
 
 ## How to add a new *public* repo for scanning by Scala Steward
 
-1. Add your repo to the list in [REPOSITORIES.md](REPOSITORIES.md)
-2. Request to [install our GitHub app](https://github.com/apps/gu-scala-steward-public-repos) on your repo
+* **Grant [our GitHub app](https://github.com/apps/gu-scala-steward-public-repos) access to your repo** (click
+  [`Configure`](https://github.com/organizations/guardian/settings/installations/26822732) - you may need
+  a repo admin to do this) 
+  * You can check if the app is installed on your repo by examining `/settings/installations`
+    (eg https://github.com/guardian/amigo/settings/installations):
+    ![image](https://github.com/guardian/scala-steward-public-repos/assets/52038/9b7dc7b7-a6fc-46d6-b313-a4ae97d5d3ad)
+* Only add your repo to `REPOSITORIES.md` if you're specifying a non-default branch to update (after
+  PR [#40](https://github.com/guardian/scala-steward-public-repos/pull/40) this is probably no longer needed).
 
 This repo (`scala-steward-public-repos`) is public, so the GitHub Action minutes are
 [free](https://docs.github.com/en/billing/managing-billing-for-github-actions/about-billing-for-github-actions).
diff --git a/REPOSITORIES.md b/REPOSITORIES.md
index 4016bba..bc7ecb4 100644
--- a/REPOSITORIES.md
+++ b/REPOSITORIES.md
@@ -1,36 +1,12 @@
+# Our Scala Steward GitHub Action will run on any repo that our GitHub App is granted access to.
+#
+# You only need to add your repo to *this* file if you're specifying a non-default branch to update.
+# Thanks to https://github.com/guardian/scala-steward-public-repos/pull/40 this is probably no longer necessary!
+
 - guardian/amiable:dependency-updates_1
 - guardian/amigo:dependency-updates
-- guardian/amiup
-- guardian/apps-rendering-api-models
-- guardian/discussion-avatar
-- guardian/google-search-indexing-observatory
-- guardian/grid-feeds
-- guardian/gu-who
-- guardian/identity-processes
-- guardian/invoicing-api
 - guardian/janus-app:dependency-updates
-- guardian/manage-help-content-publisher
-- guardian/marley
-- guardian/members-data-api
-- guardian/membership-common
-- guardian/membership-frontend
-- guardian/mobile-n10n
-- guardian/ophan-geoip-db-refresher
-- guardian/ophan-housekeeper
-- guardian/pa-football-client
-- guardian/payment-failure-comms
-- guardian/play-googleauth
-- guardian/play-secret-rotation
-- guardian/price-migration-engine
 - guardian/prism:dependency-updates
-- guardian/prout
-- guardian/repo-genesis
 - guardian/riff-raff:dependency-updates
-- guardian/salesforce-message-handler
 - guardian/security-hq:dependency-updates
 - guardian/ssm-scala:dependency-updates
-- guardian/support-frontend
-- guardian/support-service-lambdas
-- guardian/typerighter
-- guardian/zuora-6for6-modifier
-- guardian/zuora-full-export