In order to use Dropbox with Filestack, you’ll need to have your own custom Dropbox application and enter your Dropbox application’s API keys in your Filestack Developer Portal.
Go to https://www.dropbox.com/developers and click the center square labeled Create your App.
Select the radio button for Dropbox API. Choose Full Dropbox access. Name your application. Click Create App in the lower righthand corner.
On the settings tab, click the button to Enable additional users
Copy both your App key and App secret to add them to your Filestack Developer Portal later.
Add the following two redirect URIs to the section labeled OAuth 2:
Optional Step: You can configure your domain name and logo on the Branding tab.
Now you can login to your Filestack Developer Portal and find Dropbox Auth in the sidebar. Enter your App Key and App Secret from Dropbox here.