Edit your original Zap, that was created during the basic integration.
Then add an additional action to your Zapier workflow. To do this click the "+" button in between "Catch Hook" Trigger and orginal Action.
Select the additional service you would like to integrate, and follow the prompts for that service.
When making changes to a "Zap" Zapier will turn it Off while doing so. Remember to turn your Zap back on when complete!