From this drop down select Integrations....You can also find this section in your Account Settings menu under SETUP > Integrations:
To set up an integration, navigate to Account Settings > Integrations:
You'll be taken to a list of all built-in integrations that you can sort by category:
Accessing Custom Contact Fields
Moreover, DailyStory integrations, such as Mindbody, BigCommerce and more, will automatically add custom fields to your system when installed.