diff --git a/Dockerfile-postgresql b/Dockerfile-postgresql
index f8d0dc2759..15cfdc0452 100644
--- a/Dockerfile-postgresql
+++ b/Dockerfile-postgresql
@@ -1,5 +1,11 @@
-# To build run `docker build -f Dockerfile-postgresql .` from the root of the
-# zulip repo.
+# This is a multiarch Dockerfile.  See https://docs.docker.com/desktop/multi-arch/
+#
+# To set up the first time:
+#     docker buildx create --name multiarch --use
+#
+# To build:
+#     docker buildx build --platform linux/amd64,linux/arm64 \
+#       -f ./Dockerfile-postgresql -t zulip/zulip-postgresql:14 --push .
 
 # Currently the PostgreSQL images do not support automatic upgrading of
 # the on-disk data in volumes. So the base image can not currently be upgraded