You need an app for basecamp, which is not really linked anywhere but you can do them here:
https://launchpad.37signals.com/integrations
Get to your slack apps here: https://api.slack.com/apps/
Gatewood - A bridge for TODOs between Slack and Basecamp
You need an app for basecamp, which is not really linked anywhere but you can do them here:
https://launchpad.37signals.com/integrations
Get to your slack apps here: https://api.slack.com/apps/
Gatewood - A bridge for TODOs between Slack and Basecamp