Sep 18, 2021
It is really easy, summarizing, you just need to add the Bot to your group as Admin with "Delete messages" and "Ban users" rights, that's all.
Requisite: You must be the creator of that group, or an Administrator with right to be able to add other Administrators.
1 - Open group info and go to "Manage Group":
2 - Press "Administrators" to open the list of current group Admins:
3 - Press the "Add Administrator" button to add a new one:
4 - Search for @join_captcha_bot and add it (make sure to select the correct one, there could be another users instances or fake ones):
5 - You must give "Delete messages" and "Ban users" rights to allow the Bot work properly (of course you can add all rights if you want, but it is not needed):
6 - That's all, now the Bot is added and ready to keep robots out of the group!