Improve maubot doc

Add two important informations:
- The `mbc` commands must be ran in the docker container
- Not using this method prevent from using encrypted rooms with the bot

docs/configuring-playbook-bot-maubot.md

@@ -54,4 +54,5 @@ Choose a strong password for the bot. You can generate a good password with a co
 
 ## Obtaining an admin access token
 
-This can be done via `mbc auth` (see the [maubot documentation](https://docs.mau.fi/maubot/usage/cli/auth.html)). Alternatively, use Element or curl to [obtain an access token](obtaining-access-tokens.md).
+This can be done via `mbc login` then `mbc auth` (see the [maubot documentation](https://docs.mau.fi/maubot/usage/cli/auth.html)). To run these commands you'll need to open the bot docker container with `docker exec -it matrix-bot-maubot sh`
+Alternatively, use Element or curl to [obtain an access token](obtaining-access-tokens.md). However these two methods won't allow the bot to work in encrypted rooms.