release-process: explain that you need to push the branch

Signed-off-by: Maël Valais <mael@vls.dev>

content/docs/contributing/release-process.md

@@ -450,6 +450,14 @@ page if a step is missing or if it is outdated.
  [how-are-versions-of-a-sub-module-managed]:
  https://stackoverflow.com/questions/60601011/how-are-versions-of-a-sub-module-managed/60601402#60601402
 
+ Then, push the branch to your fork of cert-manager. For example:
+
+ ```bash
+ # Must be run from the cert-manager repo folder.
+ gh repo fork --remote-name fork
+ git push -u fork "update-cmd/ctl/$RELEASE_VERSION"
+ ```
+
  Then, open a PR to merge that change and go back to the release branch with
  the following commands: