diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 81fd1d7..b2f1b17 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -3,6 +3,23 @@
 How to build and test the tool, how the code is organized, and how versions and
 releases work. Back to the [README](README.md).
 
+## Sending a change
+
+New accounts on git.coffeylabs.org can file issues but can't push or fork.
+Until you have repository access, open an
+[issue](https://git.coffeylabs.org/coffey-labs/ihasmail-oneshot/issues) for the change, or say hello
+on [community.coffeylabs.org](https://community.coffeylabs.org), and attach the
+change to the issue as a patch:
+
+```sh
+git format-patch origin/main --stdout > my-change.patch
+```
+
+Repository access goes to volunteers we have worked with; a few good issues or
+patches is the usual way in. After that you push a branch here and open a pull
+request. The GitHub copy is a read-only mirror, so pull requests opened
+there are not merged.
+
 ## Building
 
 With Go 1.26.8 or newer: