You can add your bot to a chat in several ways.
Method 1 — go to Luci, open your bot’s settings, and click the “Add to chat” button.
Method 2 — open your bot’s profile and tap “Add to group or channel”.
Method 3 — copy your bot’s @username (e.g. @elfo_bot), go to the chat’s profile, tap “Add Members”, enter the username, and confirm.