Set your environment variable SLACK_API_TOKENS to one or many API tokens (comma seperated) from here: https://api.slack.com/custom-integrations/legacy-tokens
You can use a .env file. Check the file example.env, add your tokens and rename the file to .env.
Optional: change the const timeout in index.js to change the frequency
npm install
npm run start or node --use_strict index.js