docs(README): instruction to create first user

README.md

@@ -22,3 +22,13 @@
 4. `abra app YOURAPPDOMAIN config` - be sure to change `$DOMAIN` to something that resolves to
    your Docker swarm box
 5. `abra app YOURAPPDOMAIN deploy`
+
+## Create first user
+
+Run
+
+```bash
+abra app run git YOURAPPNAME gitea -c /etc/gitea/app.ini admin user create --username USERNAME --admin --random-password --email EMAIL
+```
+
+See the [Gitea command-line documentation](https://docs.gitea.io/en-us/command-line/) for more options.  Make sure not to forget the `-c /etc/gitea/app.ini`.