To connect your Slack chat channel to your 5pm account:
After you connect 5pm with Slack, others in your team can connect their 5pm accounts to the same Slack channel via "settings".
By default, you will be receiving in Slack updates on all projects and tasks create/edit/delete events (but not on any activity inside them). You can change those settings via 5pm "settings" screen. You can also limit the alerts to a specific project.
Besides getting notifications from 5pm, you can also run 5pm commands from your Slack chat — you can get the list of your tasks, close a task and even create new ones.