Slack has complicated adding bots just a bit in favor of slack apps.
BUT you can still create a classic slack app for now.
Visit https://api.slack.com/apps?new_classic_app=1 and then complete the "Create a Slack App (Classic)" form.
From there, click App Home, then click Add Legacy Bot User.
Click Install app
On the following page, if you're a slack admin, click Allow. If you're not you'll have to request approval.
Once the app is installed, under the Install App settings, copy your Bot User OAuth Access Token.
It will look like xoxb-....
Add that token to the smug.yaml file under the slack section, or set it in
your environment under SMUG_SLACK_TOKEN.
See the config.md file for more help from here.