docs(en): Add info on how to get admin rights in pleroma

content/en/docs/Services/pleroma.md

@@ -25,3 +25,14 @@ At SelfPrivacy we use [Pleroma](https://pleroma.social/).
 ## Features of Pleroma
 - A social network of any scale: from a personal server with a single account to a massive thematic site;
 - Your social network, your rules. You are the censor, moderator and administrator.
+
+## Getting admin rights
+
+Right now you can get admin rights only by using the command line.
+
+1. Connect to your server via SSH as a `root` user. Use [this guide](/docs/how-to-guides/root_ssh/) if you need help.
+2. Run the following command, replacing `<username>` with the username you want to make an admin:
+   ```
+   sudo -u pleroma env RELEASE_COOKIE=/var/lib/pleroma/.cookie pleroma_ctl user set <username> --admin
+   ```
+3. Done! Now the user `<username>` has admin rights.