add nextcloud upgrade instructions to README

README.md

@@ -450,7 +450,7 @@ helm upgrade --install \
     --create-namespace
 ```
 
-Need to copy lots of files? Copy them to the user data dir and then run
+Need to add lots of files? Copy them to the user data dir and then run
 
 ```bash
 ./occ files:scan --all
@@ -460,6 +460,20 @@ Set up SES with the following links:
 
 <https://docs.aws.amazon.com/general/latest/gr/ses.html>
 
+To upgrade you'll need to:
+
+1. Apply the new image in values.yaml
+2. Exec into the container and run the following:
+
+    ```bash
+    su -s /bin/bash www-data
+    ./occ upgrade
+    ./occ maintenance:mode --off
+    ```
+
+See <https://docs.nextcloud.com/server/latest/admin_manual/maintenance/upgrade.html#maintenance-mode>
+for more information.
+
 #### Test Deploy
 
 You can create a test deployment with the following: