1. Add the bot
Open @blackwerewolfbot and tap Add to group. @blackwwrobot runs the same game if you prefer a second bot.
2. Make it an admin
Give the bot the rights to pin and delete messages. It pins the join message so players find it, and removes old join buttons. It needs no other rights. /checksetup tells you if anything is missing.
3. Start a game
Every player opens the bot once and taps Start, so it can send them their role. Then send /startgame and wait for at least five players to join.